Friday, 3 pm, Landau Institute | hide abstracts |
Department of quantum mesoscopics: seminar, Thursday, June 23, 2022, ITF, 2:00 pm Sergei Popruzhenko (Institut obshchei fiziki im. A.M. Prokhorova RAN) Obratnyi effekt Faradeya v elektromagnitnoi volne ekstremal'noi intensivnosti Rassmotren protsess vozbuzhdeniya sil'nogo kvazistaticheskogo magnitnogo polya pri vzaimodeistvii tsirkulyarno polyarizovannoi volny vysokoi intensivnosti (10^23 Vt/sm^2 i vyshe) s plazmennym sloem. Pokazano, chto v besstolknovitel'nom rezhime vzaimodeistviya prodol'noe magnitnoe pole voznikaet za schet sily radiatsionnogo treniya. Eta spetsificheskaya realizatsiya obratnogo effekta Faradeya mozhet byt' ispol'zovana dlya poiska makroskopicheskikh proyavlenii radiatsionnogo treniya v eksperimentakh, provedenie kotorykh planiruetsya na sverkhmoshchnykh lazernykh ustanovkakh. |
[Unusual day and time!] [video] |
Department of quantum mesoscopics: seminar, Friday, May 27, 2022, ITF, 3:00 pm Pavel Maksimov (LTF im. N.N.Bogolyubova, OIYaI, Dubna) Frustrirovannyi magnetizm na primere modeli Kitaeva Frustratsiya v magnitnykh sistemakh - eto situatsiya, kogda ne vse magnitnye vzaimodeistviya mogut byt' minimizirovany klassicheski odnovremenno, i iz-za etogo razlichnye sostoyaniya mogut byt' polnost'yu vyrozhdeny. Takoe vyrozhdenie usilivaet kvantovye popravki i magnon-magnonnoe vzaimodeistvie, kotorye mogut polnost'yu razrushit' uporyadochennoe sostoyanie. Frustratsiya v dannykh sistemakh mozhet byt' vyzvana kak geometriei reshetki, tak i anizotropnymi vzaimodeistviyami. My pokazhem svoistva takikh sistem detal'no na primere predlozhennoi Alekseem Kitaevym modeli anizotropnykh vzaimodeistvii na geksagonal'noi reshetke, kotoraya otkryla put' k tochno reshaemym spinovozhidostnym fazam. |
[video] |
Department of quantum mesoscopics: seminar, Friday, April 22, 2022, ITF, 3:00 pm M. E. Ismagambetov, P. M. Ostrovskii Low-energy transport in a weakly disordered Weyl semimetal Weyl semimetal is a solid material with isolated touching points between conduction and valence bands in its Brillouin zone---Weyl points. Low energy excitations near these points exhibit a linear dispersion and act as relativistic massless particles. Weyl points are stable topological objects robust with respect to most perturbations. We study effects of weak disorder on the spectral and transport properties of Weyl semimetals in the limit of low energies. We use a model of Gaussian white-noise potential and apply dimensional regularization scheme near three dimensions to treat divergent terms in the perturbation theory. In the framework of self-consistent Born approximation, we find closed expressions for the average density of states and conductivity. Both quantities are analytic functions in the limit of zero energy. We also include interference terms beyond the self-consistent Born approximation up to the third order in disorder strength. These interference corrections are stronger than the mean-field result and non-analytic as functions of energy. Our main result is the dependence of conductivity on the electron concentration $\sigma = \sigma_0 + A n^{1/3} + (B/\sigma_0) n^{2/3} \ln|n|$ with $A \approx -0.142$ and $B \approx 0.019$. |
Department of quantum mesoscopics: seminar, Friday, March 25, 2022, ITF, 3:00 pm I. V. Bobkova Magnon-Cooparons in magnet-superconductor hybrids Generation and detection of spinfull Cooper pairs in conventional superconductors has been intensely pursued by designing increasingly complex magnet-superconductor hybrids. We demonstrate theoretically that magnons with nonzero wavenumbers universally induce a cloud of spinfull triplet Cooper pairs around them in an adjacent conventional superconductor. The resulting composite quasiparticle, termed magnon-cooparon, consists of a spin flip in the magnet screened by a cloud of the spinfull superfluid condensate. Thus, it inherits a large effective mass, which can be measured experimentally. Furthermore, we demonstrate that two magnetic wires deposited on a superconductor serve as a controllable magnonic directional coupler mediated by the nonlocal and composite nature of magnon-cooparons. Our analysis predicts a quasiparticle that enables generation, control, and use of spinfull triplet Cooper pairs in the simplest magnet-superconductor heterostructures. |
Department of quantum mesoscopics: seminar, Friday, March 18, 2022, onlain, 3:00 pm Kh.Nazaryan, L.Levitov Ustoichivost' vikhrei v potokakh elektronov Vikhri, kotorye poyavlyayutsya v potokakh elektronov, vyzyvayut interes, tak kak yavlyayutsya neoproverzhimym effektom elektronnoi gidrodinamiki. Odnako do sikh po otsutstvovala obshchaya skhema, pozvolyayushchaya svyazat' zavikhrennost', nablyudaemuyu na makrourovne, s mikroskopicheskimi mekhanizmami vzaimodeistviya i rasseyaniya. V nashei rabote my pokazyvaem, chto zavikhrennost' ustoichivym obrazom voznikaet iz-za nelokal'nosti provodimosti \sigma(k), i eto delaet zavikhrennost' svoistvom, kotoroe prisutstvuet v razlichnymi rezhimakh dvizheniya. Pri etom ballisticheskii i gidrodinamicheskii techeniya v realistichnoi geometrii dayut zavikhrennosti, blizkie po absolyutnomu znacheniyu v obeikh rezhimakh. Tem ne menee, ballisticheskie vikhri na neskol'ko poryadkov bolee ustoichivy k prisutstvii protsessov, relaksiruyushchikh impul's, chem gidrodinamicheskie vikhri. Poetomu to, kak legko vikhri gasyatsya besporyadkom i rasseyaniem fononov, mozhet sluzhit' diagnostikoi mikroskopicheskogo proiskhozhdeniya zavikhrennosti v potokakh elektronov. |
Department of quantum mesoscopics: seminar, Friday, February 25, 2022, ITF, 3:00 pm A.B. Van'kov, I.V. Kukushkin (IFTT) Kulonovskie korrelyatsii kak pervoprichina ferromagnitnogo perekhoda v rezhime kvantovogo effekta Kholla s \nu=2 Poyavivshiisya v poslednyuyu dekadu novyi tip geterostruktur na osnove ZnO/MgZnO pozvolyaet zaglyanut' v fiziku dvumernykh elektronnykh sistem (DES) sushchestvenno dal'she, chem eto bylo vozmozhno v traditsionnykh poluprovodnikakh – kremnii i arsenide galliya. Prichinoi tomu yavlyayutsya sil'nye mezhchastichnye korrelyatsii v sochetanii s malym neodnorodnym ushireniem energeticheskikh urovnei. V etikh dvumernykh sistemakh sravnitel'no legko dostigaetsya parametr Vignera-Zeitsa r_s~5–12. Pri takom nevedomom ranee sochetanii parametrov «ne rabotayut» prezhnie teoreticheskie modeli, desyatiletiyami obkatannye na dvumernom elektronnom gaze. Kachestvennuyu transformatsiyu preterpevayut dazhe «khorosho izuchennye» odnochastichnye yavleniya, takie kak tselochislennyi kvantovyi effekt Kholla (KEKh) – potomu kak vsledstvie kulonovskogo vzaimodeistviya apriori zaputannoi stanovitsya sama sistema urovnei Landau. V prezhnikh magnitotransportnykh issledovaniyakh pokazano, chto samo yavlenie KEKh v geterostrukturakh ZnO ostaetsya, odnako osnovnoe sostoyanie sistemy sil'no modifitsirovano. V dannoi rabote obnaruzhen ferromagnitnyi perekhod v rezhime tselochislennogo KEKh s chetnymi faktorami zapolneniya v sistemakh na osnove ZnO. Metodami fotolyuminestsentsii i neuprugogo rasseyaniya sveta udalos' okharakterizovat' fazovyi sostav DES, nablyudat' diapazony parametrov sistemy, otvechayushchie ferro- i paramagnitnomu uporyadocheniyu [1]. Postroena fazovaya diagramma dlya sostoyaniya KEKh \nu=2 pri izmenenii parametrov elektronnoi kontsentratsii i ugla naklona magnitnogo polya. Iz fazovoi diagrammy izvlecheny perenormirovannye fermi-zhidkostnye parametry dlya effektivnoi massy i spinovoi vospriimchivosti DES. Pokazano, chto imenno vozrastayushchaya rol' kulonovskikh korrelyatsii pri umen'shenii kontsentratsii DES yavlyaetsya pervoprichinoi dannogo fazovogo prevrashcheniya. Pomimo fenomenologii ferromagnitnogo perekhoda v nastoyashchei rabote proveden analiz mikroskopicheskogo mekhanizma etogo yavleniya. Metodom neuprugogo rasseyaniya sveta proslezheno povedenie nizkoenergeticheskikh kollektivnykh vozbuzhdenii pri izmenenii kontsentratsii DES i pokazano, chto ferromagnitnyi perekhod nastupaet vsledstvie smyagcheniya tsiklotronnogo spin-flip vozbuzhdeniya (CSFE), i posleduyushchego lavinoobraznogo perekhoda elektronov mezhdu sosednimi urovnyami Landau s protivopolozhnymi spinovymi proektsiyami [2]. Analogichno, v terminakh kollektivnykh spinovykh vozbuzhdenii ob'yasnyaetsya i obratnyi perekhod ferromagnetik-paramagnetik [3]. V oboikh sluchayakh pokazana klyuchevaya rol' nalichiya magnitorotonnogo minimuma v dispersii spinovykh vozbuzhdenii. Eksperimental'nye dannye po energii vovlechennykh kollektivnykh vozbuzhdenii khorosho soglasuyutsya s raschetom, provedennym metodami tochnoi diagonalizatsii i ekranirovannogo priblizheniya Khartri-Foka [2,3]. [1] A.B.Vankov, B.D.Kaysin, I.V.Kukushkin, Phys.Rev.B 96, 235401 (2017). |
Department of quantum mesoscopics: seminar, Friday, February 4, 2022, onlain, 3:00 pm P. S. Alekseev, A. P. Alekseeva (FTI im. A.F. Ioffe) Vyazkouprugii rezonans i poperechnye magnitozvukovye volny v vyazkoi dvumernoi elektronnoi zhidkosti V ochen' chistykh obraztsakh normal'nykh provodnikov elektrony provodimosti pri nizkikh temperaturakh mogut formirovat' vyazkuyu elektronnuyu zhidkost'. V rabote izuchayutsya vysokochastotnye techeniya takoi zhidkosti v magnitnom pole. Pokazano, chto ee koeffitsienty sdvigovoi vyazkosti imeyut rezonans pri chastote techeniya, blizkoi k udvoennoi tsiklotronnoi chastote elektronov. Takoi rezonans obuslovlen sobstvennoi dinamikoi tenzora vyazkikh napryazhenii elektricheski zaryazhennoi zhidkosti v magnitnom pole i, pri otsutstvii rezonansov na drugikh garmonikakh tsiklotronnoi chastoty, yavlyaetsya priznakom realizatsii gidrodinamicheskogo vysokochastotnogo transporta. Pokazano, chto v ochen' chistykh i dostatochno shirokikh obraztsakh predskazannyi vyazkouprugii rezonans proyavlyaetsya v koeffitsiente zatukhaniya magnitoplazmonov. Izucheny takzhe poperechnye sdvigovye magnitozvukovye volny, kotorye mogut vozbuzhdat'sya v elektronnoi zhidkosti pri dostatochno bol'shoi sile mezhchastichnogo vzaimodeistviya. V ramkakh gidrodinamicheskogo priblizheniya rasschitan ikh zakon dispersii i ikh vklad v lineinyi otklik zhidkosti na radiochastotnoe elektricheskoe pole. Chastota poperechnykh voln v predele malykh volnovykh vektorov ravna udvoennoi tsiklotronnoi chastote. Eto privodit, dlya techenii v dostatochno uzkikh obraztsakh, k proyavleniyu vyazkouprugogo rezonansa za schet komponenty techeniya, sformirovannoi magnitozvukovymi volnami. Dlya mikroskopicheskogo obosnovaniya ispol'zovannogo gidrodinamicheskogo opisaniya bylo pokazano, chto kineticheskoe uravnenie dlya vysokochastotnoi dinamiki kvazichastits elektronnoi fermi-zhidkosti v predele bol'shoi velichiny mezhchastichnogo vzaimodeistviya svoditsya k gidrodinamicheskim uravneniyam Nav'e-Stoksa s perenormirovannymi koeffitsientami. Tsiklotronnaya chastota, vkhodyashchaya v vysokochastotnuyu vyazkost' v etikh uravneniyakh, perenormiruetsya mezhchastichnym vzaimodeistviem i stanovitsya otlichnoi ot neperenormiruemoi "obychnoi" tsiklotronnoi chastoty, opredelyayushchei tsiklotronnyi rezonans. Dany argumenty v pol'zu togo, chto vozbuzhdenie izuchennykh poperechnykh magnitozvukovykh voln ob'yasnyaet anomal'nyi pik v fotosoprotivlenii naibolee kachestvennykh vysokopodvizhnykh kvantovykh yam GaAs, v kotorykh, po-vidimomu, realizuetsya gidrodinamicheskii rezhim elektronnogo transporta. |
Department of quantum mesoscopics: seminar, Friday, January 28, 2022, online, 4:00 pm Romain Vasseur (University of Massachusetts) Measurement-induced criticality An open quantum system is continuously "monitored" by its environment, so its dynamics consists of two competing processes: unitary evolution, which generates entanglement and generically leads to chaotic dynamics, and non-unitary operations resulting from measurements and noisy couplings to the environment, that tend to irreversibly destroy quantum information by revealing it. A minimal model that captures these competing processes consists of a quantum circuit made up of random unitary gates interlaced with local projective measurements. Remarkably, this minimal model undergoes a dynamical phase transition as the rate of measurements is increased. In this talk, I will introduce an exact replica statistical mechanics approach to this problem, and show that the transition is described by a CFT with central charge c=0. I will also present numerical results on the spectrum of this theory using a transfer matrix approach that indicate multifractal scaling of correlation functions at the critical point, reflected in a continuous spectrum of scaling dimensions. |
[Unusual time: 16:00] [video] |
Department of quantum mesoscopics: seminar, Friday, January 14, 2022, ITF, 4:00 pm Leonid Kulik (IFTT) Neravnovesnyi ansambl' neitral'nykh vozbuzhdenii v Laflinovskom sostoyanii 1/3 Dvumernye elektronnye sistemy v kvantuyushchem magnitnom pole predstavlyayut isklyuchitel'nyi interes s tochki zreniya vovlecheniya kvazichastits s ne bozevskoi i ne fermievskoi statistikoi (enionnoi), v oblast' prikladnykh fizicheskikh zadach. Drobnye sostoyaniya DKEKh yavlyayutsya edinstvennymi na segodnyashnii den' eksperimental'no realizovannymi kandidatami na rol' sistemy kvazichastits s enionnoi statistikoi. Dlya vyyavleniya statisticheskikh i termodinamicheskikh svoistv enionnykh sistem eksperimental'no sformirovan makroskopicheskii ansambl' neitral'nykh vozbuzhdenii v DKEKh 1/3. Okazalos', chto vozbuzhdeniya imeyut sverkhdlinnye vremena zhizni i proyavlyayut bozevskie svoistva. (Neobychnoe vremya: 16.00!) |
Department of quantum mesoscopics: seminar, Friday, January 14, 2022, onlain, 3:00 pm Vadim Shestakov (IF im. L.V. Kirenskogo) Temperaturnaya zavisimost' londonovskoi glubiny proniknoveniya magnitnogo polya pri nalichii perekhoda mezhdu sverkhprovodyashchimi sostoyaniyami s++- i s±-tipa Odnim iz glavnykh kandidatov na rol' vzaimodeistviya, privodyashchego k sverkhprovodimosti v pniktidakh i khal'kogenidakh zheleza vystupayut spinovye fluktuatsii. Oni privodyat k vozniknoveniyu sverkhprovodyashchego parametra poryadka s±-tipa. Dannoe neobychnoe sverkhprovodyashchee sostoyanie obladaet odnim zamechatel'nym svoistvom: ono mozhet pereiti v s++-sostoyanie pri uvelichenii nemagnitnogo besporyadka. Obnaruzhenie takogo perekhoda podtverdit sushchestvovanie s±-sostoyaniya v chistykh sverkhprovodnikakh na osnove zheleza i, sootvetstvenno, podtverdit spin-fluktuatsionnyi mekhanizm sverkhprovodimosti. V dannoi rabote issledovana temperaturnaya zavisimost' londonovskoi glubiny proniknoveniya v ramkakh podkhoda Eliashberga dlya dvukhzonnoi modeli s++- i s±-sverkhprovodnikov s nemagnitnymi primesyami i opredelen nabor kharakternykh osobennostei, ukazyvayushchikh na nalichie perekhoda s±→s++, a takzhe provedeno kriticheskoe sravnenie s imeyushchimisya eksperimental'nymi dannymi. |
Department of quantum mesoscopics: seminar, Friday, December 17, 2021, ITF, 3:00 pm Aleksey V. Lunkin and Mikhail V. Feigel'man High-frequency transport and zero-sound in an array of SYK quantum dots We study an array of strongly correlated quantum dots of complex SYK type and account for the effects of quadratic terms added to the SYK Hamiltonian; both local terms and inter-dot tunneling are considered in the non-Fermi-liquid temperature range T >> T_FL Electric σ(ω, p) and thermal κ(ω, p) conductivities are calculated as functions of frequency and momentum, for arbitrary values of the particle-hole asymmetry parameter. At low frequencies ω << T we find the Lorentz ratio L = κ(0, 0)/σ(0, 0) to be non-universal and temperature-dependent. At ω >> T the conductivity σ(ω, p) contains a pole with nearly linear dispersion ω ≈ sp ln (ω/T) reminiscent of the "zero-sound", known for Fermi-liquids. |
Department of quantum mesoscopics: seminar, Friday, December 10, 2021, onlain, 4:00 pm Claudio Chamon (Boston University, USA) Superconducting Circuit Realization of Combinatorial Gauge Symmetry We propose a superconducting quantum circuit based on a general symmetry principle—combinatorial gauge symmetry—designed to emulate topologically ordered quantum liquids and serve as a foundation for the construction of topological qubits. The proposed circuit exhibits rich features: in the classical limit of large capacitances its ground state consists of two superimposed loop structures; one is a crystal of small loops containing disordered U(1) degrees of freedom, and the other is a gas of loops of all sizes associated with Z2 topological order. We show that these classical results carry over to the quantum case, where phase fluctuations arise from the presence of finite capacitances, yielding Z2 quantum topological order. A key feature of the exact gauge symmetry is that amplitudes connecting different Z2 loop states arise from paths having zero classical energy cost. As a result, these amplitudes are controlled by dimensional confinement rather than tunneling through energy barriers. We argue that this effect may lead to larger energy gaps than previous proposals that are limited by such barriers, potentially making it more likely for a topological phase to be experimentally observable. Finally, we discuss how our superconducting circuit realization of combinatorial gauge symmetry can be implemented in practice. (Neobychnoe vremya: 16.00! Translyatsiya: Zoom) |
[video] |
Department of quantum mesoscopics: seminar, Friday, December 3, 2021, ITF, 3:00 pm Michael Rampp (KIT, Germany) Topologically enabled superconductivity Majorana zero modes are a much sought-after consequence of one-dimensional topological superconductivity. Here we show that, in turn, zero modes accompanying dynamical instanton events strongly enhance - in some cases even enable - superconductivity. We find that the dynamics of a one-dimensional topological triplet superconductor is governed by a theta-term in the action. For isotropic triplets, this term enables algebraic charge-2e superconductivity, which is destroyed by fluctuations in non-topological superconductors. For anisotropic triplets, zero modes suppress quantum phase slips and stabilize superconductivity over a large region of the phase diagram. We present predictions of correlation functions and thermodynamics for states of topologically enhanced superconductivity. (Translyatsiya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, November 26, 2021, ITF, 3:00 pm N. Kishmar i M. Feigel'man Teoriya dzhozefsonovskogo toka cherez izolyator Andersona bol'shoi tolshchiny Vychislen srednii dzhozefsonovskii tok I_c*\sin\phi cherez izolyator Andersona bol'shoi tolshchiny (mnogo bol'she dliny lokalizatsii \xi). Pokazano, chto amplituda toka ubyvaet priblizitel'no eksponentsial'no s tolshchinoi bar'era, odnako effektivnaya dlina ubyvaniya vo mnogo raz prevyshaet dlinu lokalizatsii elektronnykh sostoyanii v izolyatore. Tem samym, ob'yasnen davno izvestnyi eksperimental'nyi rezul'tat, izvestnyi pod nazvaniem "long range Josephson effect". Razvitaya teoriya pokazyvaet chto kachestvenno etot effekt svyazan s a) sil'nymi fluktuatsiyami volnovykh funktsii lokalizovannykh sostoyanii, i b) mottovskimi rezonansami na parakh lokalizovannykh sostoyanii. Pokazano, chto pri tolshchine izolyatora L bol'she "mottovskoi dliny" L_M = \xi \ln(\delta_\xi/\Delta) izmenyaetsya znak amplitudy toka I_c, to est' realizuetsya sverkhprovodyashchii "pi-kontakt". (Translyatsiya: Zoom) |
[video] |
Department of quantum mesoscopics: seminar, Friday, November 12, 2021, ITF, 3:00 pm Aleksei Dmitriev (aspirant Laboratorii iskustvennykh kvantovykh sistem MFTI) Doklad po materialam kandidatskoi dissertatsii "Issledovanie nelineinykh kvantovo-opticheskikh effektov pri rasseyanii sveta na sverkhprovodnikovom kubite v odnomernom prostranstve" (Translyatsiya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, November 5, 2021, ITF, 11:00 am Gleb Fedorov (aspirant Laboratorii iskustvennykh kvantovykh sistem MFTI) Doklad po materialam dissertatsii "Modelirovanie kvantovogo vzaimodeistviya izlucheniya i veshchestva s ispol'zovaniem massivov sverkhprovodnikovykh iskusstvennykh atomov" (Neobychnoe vremya: 11.00! Translyatsiya: Zoom) |
[video] |
Department of quantum mesoscopics: seminar, Friday, October 29, 2021, onlain, 11:30 am K. S. Tikhonov Mnogochastichnaya lokalizatsiya: obzor razlichnykh rezul'tatov (Neobychnoe vremya: 11.30! Translyatsiya: Zoom) In the first part, I will briefly summarize our current understanding of the relation between Anderson localization on random regular graphs and many-body localization (MBL) [1]. In the second part, I will review several recent preprints, which question observability of genuine MBL transition in state-of-the-art numerical simulations [2,3,4]. [1] Tikhonov, Mirlin; Annals of Physics, 168525 |
Department of quantum mesoscopics: seminar, Friday, October 22, 2021, ITF, 3:00 pm V. S. Khrapai (IFTT) Razdelenie tepla i zaryada v trekhterminal'noi NSN strukture iz nanoprovoloki InAs (Ceminar v normal'nom rezhime, s translyatsiei: Zoom) V samoe poslednee vremya nablyudaetsya interes k nelokal'nomu kvazichastichnomu otkliku v strukturakh s maioranovskimi nanoprovolokami [1]. Predpolagaetsya, chto issledovanie nelokal'noi provodimosti pomozhet prolit' svet na proiskhozhdenie podshchelevogo transporta i nadezhno ustanovit' tochku topologicheskogo fazovogo perekhoda. Ya rasskazhu ob eksperimente [2], postavlennom v trivial'noi faze i demonstriruyushchem vtorichnost' nelokal'noi provodimosti po sravneniyu s nelokal'nym teplovym otklikom. V osnove eksperimenta lezhit sochetanie nelokal'nogo transporta s nelokal'nym shumovym otklikom, pozvolivshee prodemonstrirovat' effektivnoe razdelenie tepla i zaryada na sverkhprovodyashchem kontakte. V rezul'tate takogo razdeleniya srednii zaryad proshedshei kvazichastitsy okazyvaetsya blizok k nulyu, tak chto nelokal'nyi kvazichastichnyi transport yavlyaetsya zaryadovo-neitral'nym. Krome togo, nablyudenie predskazannogo nedavno Andreevskogo vypryamleniya [3] demonstriruet, chto etot effekt ne yavlyaetsya unikal'nym svoistvom topolicheskogo fazovogo perekhoda. [1] D. Puglia et al., Phys. Rev. B 103, 235201 (2021) https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.235201 [2] A.O. Denisov et al., Semicond. Sci. Tech., 36, 09LT04 (2021) https://iopscience.iop.org/article/10.1088/1361-6641/ac187b/meta [3] T.Ö. Rosdahl et al., Phys. Rev. B 97, 045421 (2018) https://journals.aps.org/prb/abstract/10.1103/PhysRevB.97.045421 |
Department of quantum mesoscopics: seminar, Friday, October 15, 2021, online, 4:00 pm Anton Andreev Electronic pumping of heat in absence of charge pumping A mechanism of electron-mediated pumping of heat in the absence of net charge transfer is proposed. It may be realized in charge-neutral electron systems, such as graphene, coupled to an external electric potential. The flow of heat in this pumping cycle is not accompanied by a buildup of voltage along the system, which offers advantages over traditional thermoelectric cooling setups. Efficiency of heat pumping and magnitude of heat flux are studied in the hydrodynamic regime for weak disorder. In a pristine system, even for an infinitesimal pumping potential the heat flux remains finite. In particular, for a potential in the form of a traveling wave moving with velocity c the pumping is perfect; the entire heat content of the electron liquid is advected with velocity c. For a general pumping cycle the heat flux is determined by the cycle geometry and disorder strength. |
Department of quantum mesoscopics: seminar, Friday, June 4, 2021, ITF, 4:15 pm A.S. Osin and Ya.V. Fominov Superconducting phases and the second Josephson harmonic in tunnel junctions between diffusive superconductors (Ceminar v normal'nom rezhime, s translyatsiei: Zoom) |
Department of quantum mesoscopics: seminar, Friday, June 4, 2021, onlain, 3:00 pm Ivan Khaimovich Localization beyond convergence of the locator expansion or Correlation-induced localization Recently, the standard picture of ALT in long-range systems [1, 2] has been argued from the following perspective. There have been reported [3-6] several counterintuitive examples of single-particle systems with long-range hopping, where almost all states are (at least power-law) localized even in a nominally ergodic regime, where the standard locator expansion breaks down [1, 2]. Some of these "new" models demonstrate critical behavior [3, 4] for disorder strengths below the ones at the ALT [1, 2]. In the other ones [6, 7] wave-function spatial decay rates obey a "mysterious" duality [6] mapping different powers of power-law bending [2]. The seminal paper on second-type models [7] has been unnoticed until recently.
|
Department of quantum mesoscopics: seminar, Friday, May 28, 2021, ITF, 4:15 pm A. V. Lunkin and M. V. Feigel’man Non-equilibrium Sachdev-Ye-Kitaev model with quadratic perturbation (Seminar v normal'nom rezhime, s translyatsiei: Zoom) |
Department of quantum mesoscopics: seminar, Friday, May 28, 2021, onlain, 3:00 pm Milan P. Allan (TU Delft) Direct evidence for Cooper pairing without a spectral gap in a disordered superconductors above Tc (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, May 21, 2021, ITF, 3:00 pm V. Zyuzin Neustoichivost' nakachennykh dirakovskikh magnonnykh par (Ceminar v normal'nom rezhime, s translyatsiei: Zoom) |
Department of quantum mesoscopics: seminar, Friday, May 14, 2021, ITF, 3:00 pm Ul'yana Khodaeva Struktura vikhrya v chistom sverkhprovodnike vblizi ploskogo defekta (Ceminar v normal'nom rezhime, s translyatsiei: Zoom) |
Department of quantum mesoscopics: seminar, Friday, April 30, 2021, onlain, 5:30 pm V.A.Zakharov i I.S.Burmistrov Ostatochnaya ob'emnaya vyazkost' dvumernogo elektronnogo gaza s besporyadkom (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, April 30, 2021, onlain, 4:30 pm E.S.Andriyakhina i I.S.Burmistrov Vzaimodeistvie neelevskogo skirmiona i pirlovskogo vikhrya (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, April 23, 2021, online, 5:00 pm Lara Faoro and Lev Ioffe Critical behavior of surface code statistical models (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, April 9, 2021, ITF, 3:00 pm Anton Khvalyuk, Konstantin Kechedzhi Analiticheskaya teoriya k nekotorym ne-integriruemym diskretnym kvantovym skhemam konechnogo razmera v prisutstvii shuma (Ceminar v normal'nom rezhime, s translyatsiei: Zoom) |
Department of quantum mesoscopics: seminar, Friday, April 2, 2021, onlain, 5:00 pm Kostya Kechedzhi (Google AI Quantum, Venice, California, USA) Quantum circuit kinetics of programmable quantum computers (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, March 26, 2021, onlain, 4:30 pm Boris Spivak Propagation of nonlinear waves in disordered media (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, March 26, 2021, ITF, 3:00 pm Viktor Galitskii Many-Body Level Statistics of Single-Particle Quantum Chaos (Obychnyi doklad s onlain translyatsiei: Zoom) |
Department of quantum mesoscopics: seminar, Friday, February 26, 2021, onlain, 3:00 pm Khachatur Nazaryan i Mikhail Feigel'man Conductivity and thermoelectric coefficients of doped SrTiO3 at high temperatures (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, February 5, 2021, onlain, 3:00 pm Konstantin Tikhonov Obobshchayushchaya sposobnost' neirosetevykh variatsionnykh anzatsev dlya frustrirovannykh magnitnykh sistem (podrobnoe izlozhenie raboty, kratko predstavlennoi na US ITF 4 dekabrya 2020) (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, January 29, 2021, onlain, 3:00 pm Egor Kiselev (Karlsruhe Institute of Technology) Dirac liquids: phase space dynamics, non-local transport properties and collective excitations (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, January 15, 2021, onlain, 3:00 pm Vladimir Zyuzin Nechetnoe po chastote sparivanie v neuporyadochennykh provodnikakh (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, December 18, 2020, onlain, 4:00 pm Leonid Glazman (Yale University) Critical fluorescence of a transmon at the Schmid transition (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, December 11, 2020, onlain, 4:00 pm Vladislav Kurilovich (Yale University) Quantum-critical dynamics of a Josephson junction at the topological transition (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, November 27, 2020, onlain, 3:00 pm K.S. Tikhonov Doklad po zadacham v rabote (Nazhmite dlya podklyucheniya: Zoom)
|
Department of quantum mesoscopics: seminar, Friday, November 13, 2020, onlain, 3:00 pm Nicolas Roch, Benjamin Sacepe, Thibault Charpentier (Neel Institute, Grenoble) The fate of the superfluid density near the SIT in amorphous superconductors (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, October 30, 2020, onlain, 3:00 pm Leonid Golub, Mikhail Glazov (FTI im.A.F.Ioffe) Dolinnyi effekt Kholla v usloviyakh effekta uvlecheniya (Nazhmite dlya podklyucheniya: Zoom) |
Department of quantum mesoscopics: seminar, Friday, October 16, 2020, ITF, 3:00 pm M.A. Skvortsov Doklad po zadacham v rabote
|
Department of quantum mesoscopics: seminar, Friday, October 2, 2020, ITF, 3:00 pm I.S. Burmistrov Doklad po zadacham v rabote
Seminar ochnyi, no s online translyatsiei dlya interesuyushchikhsya, no otsutstvuyushchikh: link na translyatsiyu |
Department of quantum mesoscopics: seminar, Friday, September 25, 2020, ITF, 3:00 pm M.V. Feigel'man Doklad M.Feigel'mana s obzorom raznykh reshaemykh seichas s razlichnymi kollegami zadach Fail s prezentatsiei: zdes' |
Department of quantum mesoscopics: seminar, Friday, May 29, 2020, webinar, 3:00 pm Vladimir Kravtsov Fragile ergodic phases in logarithmically-normal Rosenzweig-Porter model Webinar link: http://bbb2.itp.ac.ru/b/qme-erf-krk
|
Department of quantum mesoscopics: seminar, Friday, May 22, 2020, webinar, 3:00 pm A.V. Lunkin, A.Yu. Kitaev, M.V. Feigel'man Sachdev-Ye-Kitaev model with perturbations: polaron in hyperbolic plane Webinar link: http://bbb2.itp.ac.ru/b/qme-erf-krk
|
Department of quantum mesoscopics: seminar, Friday, May 8, 2020, webinar, 3:00 pm A. V. Andreev, Steven A. Kivelson, B. Spivak Hydrodynamic description of transport in strongly correlated electron systems Webinar link: http://bbb2.itp.ac.ru/b/qme-erf-krk
|
Department of quantum mesoscopics: seminar, Friday, May 1, 2020, webinar, 3:00 pm Zvi Ovadyahu (Hebrew University of Jerusalem) Long-range influence of manipulating disordered-insulators locally Webinar: http://bbb2.itp.ac.ru/b/qme-erf-krk
|
Department of quantum mesoscopics: seminar, Friday, April 24, 2020, webinar, 4:00 pm Grigory Tarnopolsky (Harvard University) Fractional Chern Insulator States in Twisted Bilayer Graphene Webinar: http://bbb2.itp.ac.ru/b/qme-erf-krk
|
Department of quantum mesoscopics: seminar, Friday, April 10, 2020, webinar, 4:00 pm Elio Koenig (Rutgers University) Soluble limit and criticality of fermions in Z2 gauge theories Webinar: http://bbb2.itp.ac.ru/b/qme-erf-krk
|
Department of quantum mesoscopics: seminar, Friday, February 14, 2020, ITF, 3:30 pm M.Feigel'man i K.Tikhonov Strange metal state near quantum superconductor-metal transition in thin films We develop a theory of quantum T = 0 phase transition (q-SMT) between metal and superconducting ground states in a two-dimensional metal with frozen-in spatial fluctuations δλ(r) of the Cooper attraction constant. When strength of fluctuations δλ(r) exceeds some critical magnitude, usual mean-field-like scenario of the q-SMT breaks down due to spontaneous formation of local droplets of superconducting phase. The density of these droplets grows exponentially with the increase of average attraction constant λ. Interaction between the droplet's order parameters is due to proximity effect via normal metal and scales with distance ∝ 1/rβ, with 2 < β ≤ 3. We account for this interaction by means of a real-space strong-disorder renormalization group (RG). Near the q-SMT the RG flow is, formally, a dual equivalent of the Kosterlitz-Thouless RG. The corresponding line of fixed points describes a Griffiths phase of a metal with large fractal clusters of superconducting islands. Superconducting side is described by a runaway of RG trajectories into the strong-coupling region. Close to the transition point on the SC side, 0 < −δ << 1, RG trajectories possess an extremum as function of the RG parameter ∼ |δ| 1/2 ln(1/T). It results in a very wide temperature range where physical properties are nearly T-independent. This observation may be relevant to the understanding of a ”strange metal” state frequently observed near q-SMT. |
Department of quantum mesoscopics: seminar, Friday, February 7, 2020, ITF, 3:00 pm A.N. Poddubnyi (FTI im.A.F.Ioffe) Vzaimodeistvie dvukh fotonov s massivom atomov v volnovode Rassmatrivaetsya teoreticheskaya zadacha o rasprostranenii pary fotonov v odnomernom volnovode, v kotoryi pomeshchen periodicheskii massiv dvukhurovnevykh atomov. Otlichiem ot klassicheskoi modeli Dikke yavlyaetsya uchet konechnogo nenulevogo rasstoyaniya mezhdu atomami. Blagodarya fotonnoi blokade - nevozmozhnosti pogloshcheniya dvukh fotonov odnim atomom - mezhdu fotonami voznikaet effektivnoe ottalkivanie. Budet pokazano, chto eto ottalkivanie privodit k obrazovaniyu dvukhfotonnykh sostoyanii, kogda odin iz fotonov lokalizovan, a vtoroi obrazuet stoyachuyu volnu. Takie dvukhchastichnye mody mozhno rassmatrivat' kak analog indutsirovannykh vzaimodeistviem opticheskikh reshetok. |
Department of quantum mesoscopics: seminar, Friday, December 13, 2019, ITF, 3:30 pm 2. Anton Khvalyuk Obzor osnovnykh algoritmov kvantovykh simulyatsii Iz-za apparatnykh ogranichenii sushchestvuyushchie kvantovye protsessory sposobny proizvodit' lish' opredelennyi nabor unitarnykh operatsii nad odnim ili dvumya kvantovymi bitami v techenie konechnogo promezhutka vremeni, posle kotorogo ustroistvo teryaet kogerentnost'. Chtoby ispol'zovat' podobnye ustroistva dlya simulyatsii proizvol'nogo vida gamil'tonianov, neobkhodimo stroit' priblizheniya, pozvolyayushchie s pomoshch'yu dostupnykh operatsii vosproizvesti proizvol'nyi operator evolyutsii i pri etom ispol'zuyushchie kak mozhno men'she obrashchenii k kvantovomu ustroistvu.
My razberem detali raboty kazhdogo iz predstavlennykh algoritmov, obsudim sushchestvuyushchie otsenki dlya ikh vremeni raboty i chisla ispol'zuemykh elementarnykh operatsii. |
Department of quantum mesoscopics: seminar, Friday, December 13, 2019, ITF, 2:30 pm 1. Ivan Tsitsilin (MISiS, RKTs) Eksperimenty so sverkhprovodyashchimi kubitami Razvitie tekhnologii proizvodstva i izmereniya sverkhprovodyashchikh kubitov v Rossii uzhe pozvolyaet sozdavat' mnogokubitnye svyazannye sistemy, iz kotorykh mozhno delat' razlichnye analogovye i tsifrovye simulyatory. Poluchennyi v sozdanii dvukhkubitnykh geitov opyt pokazal nam napravlenie dlya dal'neishego razvitiya v etoi sfere: kakie tipy geitov neobkhodimo ispol'zovat' i uluchshat', kak vyklyuchat' ostatochnoe ZZ vzaimodeistvie vo vremya prostaivaniya kubitov. Ya predstavlyu nashi rezul'taty i rasskazhu o potentsial'nykh sposobakh prodvizheniya v etikh oblastyakh. |
Department of quantum mesoscopics: seminar, Friday, November 29, 2019, ITF, 3:00 pm V.Kuznetsov (eksperimental'naya chast') i S.Dikman (teoreticheskaya chast') Sovmestnyi doklad po rabote S.Dikmana, L.Kulika i V.Kuznetsova (IFTT) "Coherence-decoherence transition in a spin-magnetoexcitonic ensemble in a quantum Hall system" In the talk, we focus on the physics of magneto-excitons in a quantum
Hall insulator at the filling factor of 2. The simplest realizations are
magneto-excitons formed by an electron promoted from the occupied zeroth
Landau level to the empty first Landau level and by the vacancy under
the Fermi level. There are two magneto-excitons: a spin-singlet with
total spin S = 0; and a spin-triplet (CSFE) with total spin S = 1. The
first one is magneto-plasmon which decays with the emission of a photon.
In contrast, the CSFE is not radiatively active owing to electron spin
conservation and its energy is lower than the cyclotron energy.
Consequently, spin-triplet magneto-excitons exhibit relaxation time
reaching up to 900 us. We also discovered condensation of excitons by
measurement of exciton lifetime in a temperature range of 0.5–1.5 K.
Here we report on spin exciton transfer at distance exceeding 200 μm by
pump-probe photo-luminescence measurements and photo-resonant reflection.
These effects exhibit threshold both in excitation power and
temperature. |
Department of quantum mesoscopics: seminar, Friday, November 1, 2019, ITF, 3:00 pm Vasilii Vadimov (IFM, Nizhnii Novgorod) Mody Khiggsa v gibridnykh sistemakh sverkhprovodnik-normal'nyi metall Effekt blizosti v gibridnykh sistemakh sverkhprovodnik-normal'nyi metall okazyvaet sushchestvennoe vliyanie na kogerentnye kolebaniya sverkhprovodyashchego parametra poryadka Δ, izvestnye kak mody Khiggsa. Standartnaya moda Khiggsa s chastotoi 2Δ ispytyvaet zatukhanie iz-za utechki kvazichastits iz sverkhprovodnika v normal'nyi metall. Pomimo etogo iz-za kogerentnogo tunnelirovaniya elektronov mezhdu sverkhprovodnikom i normal'nym metallom poyavlyayutsya dve dopolnitel'nye khiggsovskie mody s chastotami, opredelyaemymi pervichnoi shchel'yu Δ i navedennoi shchel'yu v normal'nom metalle. Eti tri mody opredelyayut asimptoticheskoe povedenie sverkhprovodyashchego parametra poryadka, vozmushchennogo elektromagnitnym impul'som libo rezkim izmeneniem parametrov sistemy. Issledovanie mod Khiggsa v gibridnykh strukturakh vazhno dlya ponimaniya dinamicheskikh svoistv sverkhprovodyashchikh priborov, osnovannykh na effekte blizosti. |
Department of quantum mesoscopics: seminar, Friday, May 17, 2019, ITF, 3:00 pm Anton Khvalyuk Simple model for describing trotterization effects in quantum simulations Kvantovye vychisleniya v poslednee vremya yavlyayutsya aktivno razvivayushcheisya oblast'yu prikladnoi fiziki i teorii informatsii. Odnim iz mnogoobeshchayushchikh primenenii vozmozhnostei segodnyashnikh kvantovykh komp'yuterov yavlyayutsya kvantovyi simulyatsii fizicheskikh sistem na sistemakh kubitov. Odnako, sushchestvennymi problemami na puti k fizicheski korrektnym simulyatsiyam yavlyayutsya trotterovskaya oshibka diskretizatsii i razlichnye effekty shuma. V etom doklade budet predlozhena prostaya tochno reshaemaya model' sistemy spinov, pozvolyayushchaya izuchit' osnovnye effekty trotterovskoi oshibki i dayushchaya vozmozhnost' dlya izucheniya effektov shuma. |
Department of quantum mesoscopics: seminar, Friday, April 5, 2019, ITF, 3:00 pm Tim Ludwig (Karlsruhe Institute of Technology) Noise of charge current generated by driven magnet We determine the noise of charge current that is generated by a precessing magnetization of a small itinerant ferromagnet, which is driven by ferromagnetic resonance (FMR) and tunnel-coupled to two normal metal leads. Even when the leads are in equilibrium with each other, i.e. neither voltage nor thermal bias is applied, the electron system is driven out of equilibrium by the precessing magnetization. In turn, a non-equilibrium electron distribution develops in the small ferromagnet. This distribution is governed by the dynamics of the magnetization and determines the (zero-frequency) noise of charge current. We show that this noise can be used to gain information about the magnetization dynamics. |
Department of quantum mesoscopics: seminar, Friday, March 15, 2019, ITF, 3:00 pm A.V. Lunkin Geometricheskii podkhod k resheniyu SYK (po motivam izucheniya stat'i A.Yu. Kitaeva) |
Department of quantum mesoscopics: seminar, Friday, March 1, 2019, ITF, 3:00 pm A.V. Poshakinskii, A.N. Poddubnyi (FTI im. A.F. Ioffe) Rasseyanie sveta na drozhashchikh telakh s rezonansnoi dielektricheskoi pronitsaemost'yu Postroena teoriya, opisyvayushchaya vzaimodeistvie elektromagnitnogo polya s drozhashchei dispergiruyushchei sredoi. V pervom poryadke po mekhanicheskomu smeshcheniyu vychislena popravka k polyarizuemosti sredy, obuslovlennaya drozhaniem. Pokazano, chto dvizhenie v prostranstve elektricheskogo dipolya privodit k poyavleniyu magnitnogo dipol'nogo i elektricheskogo kvadrupol'nogo momentov. Teoriya primenena dlya opisaniya neuprugogo rasseyaniya sveta na drozhashchikh chastitsakh i membranakh. Ustanovleno, chto kharakter interferentsii elektromagnitnykh voln, izluchennykh razlichnymi mul'tipolyami, opredelyaetsya chastotnoi zavisimost'yu dielektricheskoi pronitsaemosti. V sluchae, kogda ona imeet rezonans, vblizi nego svet rasseivaetsya preimushchestvenno vpered, a vdali ot nego — nazad. Takzhe opisana konversiya polyarizatsii sveta v protsesse neuprugogo rasseyaniya. |
Department of quantum mesoscopics: seminar, Friday, February 15, 2019, ITF, 3:00 pm Mariya Kostenko (SPbGU) Anomal'nyi skeiling v turbulentnosti: renormgruppovoi podkhod V doklade budet obsuzhdat'sya zadacha ob anomal'nom skeilinge v turbulentnosti. Eto yavlenie proyavlyaetsya v singulyarnom (vozmozhno stepennom) povedenii razlichnykh statisticheskikh velichin, zavisyashchikh ot integral'nogo masshtaba turbulentnosti s beskonechnym kolichestvom nezavisimykh anomal'nykh pokazatelei. I eksperimenty, i chislennoe modelirovanie pokazyvayut, chto otkloneniya ot klassicheskoi teorii Kolmogorova bolee yarko vyrazheny dlya passivnogo perenosa skalyarnykh polei (naprimer, polya temperatury ili plotnosti primesi), chem dlya samogo polya skorosti. Samyi znachitel'nyi progress byl dostignut dlya modeli Kreichnana, gde pole skorostei perenosa yavlyaetsya gaussovym, ne korrelirovannym po vremeni. V protsesse doklada budet podrobno obsuzhdat'sya metod renormgruppy v primenenii k etoi modeli, a takzhe k bolee slozhnym i realistichnym modelyam perenosa. |
Department of quantum mesoscopics: seminar, Friday, February 8, 2019, ITF, 3:00 pm V.V. Marinyuk, D.B. Rogozkin (MIFI) Mezoskopicheskie fluktuatsii kondaktansa na subdiffuzionnykh masshtabakh V ramkakh diagrammnoi tekhniki vyvoditsya analiticheskoe vyrazhenie dlya dispersii kondaktansa neuporyadochennogo obraztsa cherez propagatory, podchinyayushchiesya transportnomu uravneniyu. Vychisleniya osnovany na sootnosheniyakh dlya vershiny Khikami bez ispol'zovaniya diffuzionnogo (gradientnogo) razlozheniya i bornovskogo priblizheniya dlya odnotsentrovogo rasseyaniya. Obsuzhdayutsya prichiny usileniya fluktuatsii pri perekhode ot kvaziballisticheskogo k diffuzionnomu rezhimu transporta. |
Department of quantum mesoscopics: seminar, Friday, January 18, 2019, ITF, 3:00 pm N.E. Nefedkin, A.A. Zyablovskii, E.S. Andrianov, A.A. Pukhov, A.P. Vinogradov (VNII Avtomatiki im. N.L. Dukhova) Kooperatsiya mod v dvumernykh plazmonnykh lazerakh s raspredelennoi obratnoi svyaz'yu Issledovana dinamika plazmonnogo lazera s raspredelennoi obratnoi svyaz'yu (DFB lazera) na osnove dvumernoi perforirovannoi metallicheskoi plenki. Dlya takoi struktury mozhno vydelit' dva kharakternykh tipa mod. K pervomu iz nikh otnosyatsya mody, chastota kotorykh nakhoditsya v razreshennoi zone, imeyushchie bol'shie izluchatel'nye poteri i vysokii porog generatsii (svetlye mody). Ko vtoromu tipu otnosyatsya mody, chastota kotorykh nakhoditsya na krayu razreshennoi zony, imeyushchie nizkie izluchatel'nye poteri i nizkii porog generatsii (temnye mody). Pokazano, chto kogda pyatno nakachki men'she razmera poverkhnosti DFB lazera, nelineinoe vzaimodeistvie mezhdu modami periodicheskoi plazmonnoi struktury cherez aktivnuyu sredu privodit k novomu effektu, a imenno k kooperatsii mod [1]. Kooperatsiya mod proyavlyaetsya kak generatsiya svetlykh mod s vysokimi poteryami vmesto generatsii temnykh mod s nizkimi poteryami. Pokazano, chto etot effekt imeet mesto v dvumernykh DFB lazerakh i ne proyavlyaetsya v odnomernykh DFB lazerakh. Vzaimodeistvie svetlykh mod voznikaet iz-za neortogonal'nosti lazernykh mod v oblasti nakachki, gde svetlye mody stanovyatsya sinkhronizirovannymi po faze. Kak sledstvie, voznikaet ikh konstruktivnaya interferentsiya. Prodemonstrirovano, chto vsledstvie kooperatsii mod imeet mesto ushirenie diagrammy napravlennosti vyshe poroga generatsii, chto nablyudalos' v nedavnikh eksperimentakh [2]. [1] N.E. Nefedkin, A.A. Zyablovsky, E.S. Andrianov, A.A. Pukhov, and A. P. Vinogradov, ACS Photonics 2018 5(8): p. 3031-3039. |
Department of quantum mesoscopics: seminar, Friday, December 21, 2018, ITF, 3:00 pm A.S. Petrov, D.A. Svintsov (Laboratoriya optoelektroniki dvumernykh materialov MFTI) Teoriya vozmushchenii dlya gidrodinamicheskikh plazmennykh effektov v dvumernykh elektronnykh sistemakh V doklade budet predstavlen odin iz metodov dlya opisaniya gidrodinamicheskikh plazmennykh effektov v dvumernykh elektronnykh sistemakh (DES). A imenno, budet primenen operatornyi podkhod k uravneniyam elektronnoi gidrodinamiki i postroen analog kvantovo-mekhanicheskoi teorii vozmushchenii. Razrabotannaya teoriya pozvolit poluchit' vyrazhenie dlya pervoi popravki k sobstvennoi chastote plazmonov v prisutstvie slabogo dreifa nositelei, magnitnogo polya, vyazkosti i rasseyaniya na primesyakh. Na model'nykh primerakh budet vyyavlen kharakter vliyaniya etikh vozmushchenii na spektr i ustoichivost' plazmennykh voln v razlichnykh strukturakh. Tak, budut opredeleny: (1) obshchie svoistva tokovykh neustoichivostei v ogranichennykh DES, (2) vliyanie dreifa nositelei na spektr plazmonov v periodicheskikh DES (usilennyi effekt Doplera), i (3) mekhanizmy vozbuzhdeniya kraevykh mod postoyannym tokom. |
Department of quantum mesoscopics: seminar, Friday, December 14, 2018, ITF, 3:00 pm Dmitrii Smirnov (Fiziko-tekhnicheskii institut im. A.F. Ioffe) Spektroskopiya spinovykh i zaryadovykh fluktuatsii v odinochnoi kvantovoi tochke Razvita teoriya opticheskoi spektroskopii neravnovesnykh spinovykh i zaryadovykh fluktuatsii v kvantovoi tochke, pomeshchennoi v mikrorezonator. Pokazano, chto v rezhime sil'noi svyazi fotonnoi mody mikrorezonatora s trionnym rezonansom kvantovoi tochki fluktuatsii koeffitsienta prokhozhdeniya sveta cherez mikrorezonator soderzhat informatsiyu kak o spinovoi dinamike sistemy, tak i o statistike fotonov v mikrorezonatore. V rezhime slaboi svyazi vozmozhno formirovanie "odetykh fotonami" sostoyanii, chto pozvolyaet opredelyat' parametry spinovoi spinovoi dinamiki ne tol'ko dlya osnovnogo, no i dlya vozbuzhdennogo sostoyaniya kvantovoi tochki po fluktuatsiyam opticheskikh signalov Faradeya ili Kerra. Prilozhenie k sisteme prodol'nogo magnitnogo polya privodit k vozmozhnosti detektirovaniya zaryadovykh fluktuatsii v kvantovoi tochke. |
Department of quantum mesoscopics: seminar, Friday, December 7, 2018, ITF, 3:00 pm W. Belzig (Univ. of Konstanz) Topological effects in multi-terminal Josephson proximity systems This will include e.g. works like |
Department of quantum mesoscopics: seminar, Friday, June 9, 2017, ITF, 3:00 pm V. V. Enaldiev (IRE RAS) Resonance Absorption of Terahertz Radiation in Nanoperforated Graphene Recent measurements of the conductivity of nanoperforated graphene are interpreted in terms of edges states existing near the edge of each nanohole. The perimetric quantization of edge states should result in the formation of a quasi-equidistant ladder of quasistationary energy levels. Dirac fermions filling this ladder rotate about each nanohole in the direction determined by the valley index. We show that the irradiation of this system by circularly polarized terahertz radiation leads to a resonance in absorption in one of the valleys. The magnitude of absorption at the resonance frequency can be controlled by means of gate voltage. |
Department of quantum mesoscopics: seminar, Friday, June 3, 2016, ITF, 4:00 pm A. P. Dmitriev (FTI im. A. F. Ioffe) Elektron v pole izgibnykh kolebanii membrany: kvantovoe vremya, magneto-ostsillyatsii i razrushenie kogerentnosti Izucheno dvizhenie elektrona v membrane pod vliyaniem ravnovesnykh izgibnykh kolebanii, korrelyator kotorykh ubyvaet s rasstoyaniem po zakonu r^{-2\eta}. Podrobno rassmotren sluchai \eta<1/2, kogda dazhe pri skol' ugodno slabom vzaimodeistvii teoriya vozmushchenii neprimenima. Pokazano, chto v etom sluchae obratnoe kvantovoe vremya proportsional'no g^{1/(1-\eta)} T^{(2-\eta)/(2-2\eta)}, gde g - konstanta elektron-fononnogo vzaimodeistviya, a T - temperatura. Razvityi metod prilozhen k vychisleniyu plotnosti sostoyanii elektrona v perpendikulyarnom k membrane magnitnom pole. Pokazano, v chastnosti, chto v rezhime slaboushirennykh besporyadkom urovnei Landau oni imeyut gaussovu formu s shirinoi, zavisyashchei ot magnitnogo polya po zakonu B^\eta. Krome togo, vychisleno vremya sboya fazy volnovoi funktsii elektrona za schet ego vzaimodeistviya s izgibnymi fononami v sluchae \eta<1/2. Pokazano, chto imeetsya neskol'ko temperaturnykh intervalov, v kotorykh vremya sboya fazy vyrazhaetsya razlichnymi stepennymi funktsiyami ot konstanty elektron-fononnogo vzaimodeistviya, temperatury i energii elektrona. |
Department of quantum mesoscopics: seminar, Friday, June 3, 2016, ITF, 2:30 pm A. V. Semenov (MGPU) Coherent excited states in superconductors due to a microwave field We describe theoretically the depairing effect of a microwave field on diffusive s-wave superconductors. The ground state of the superconductor is altered qualitatively in analogy to the depairing due to a dc current. In contrast to dc-depairing the density of states acquires, for microwaves with frequency \omega_0, steps at multiples of the photon energy \Delta \pm n\hbar\omega_0 and shows an exponential-like tail in the subgap regime. We show that this ac-depairing explains the measured frequency shift of a superconducting resonator at high microwave power and low temperatures. |
Department of quantum mesoscopics: seminar, Friday, April 22, 2016, ITF, 3:00 pm D. M. Basko (CNRS, Grenoble) O roli effekta Landau-Zinera v rabote kvantovogo turniketa Kvantovyi turniket predstavlyaet soboi nanoelektronnoe ustroistvo, kontroliruemym obrazom perenosyashchee elektrony po odnomu mezhdu dvumya sverkhprovodyashchimi elektrodami putem podachi peremennogo napryazheniya na metallicheskuyu nanochastitsu, raspolozhennuyu mezhdu dvumya elektrodami. Okazyvaetsya, chto kogerentnaya svyaz' mezhdu elektronnymi sostoyaniyami v nanochastitse i kvazichastichnymi sostoyaniyami v sverkhprovodnikakh nakladyvaet fundamental'nye ogranicheniya na rabotu ustroistva. |
Department of quantum mesoscopics: seminar, Friday, April 15, 2016, ITF, 3:00 pm M. V. Feigel'man Quantum tunneling vs. thermal effects in experiments on adiabatic quantum computing Referativnyi doklad po rabote D. M. Silevitch, T. F. Rosenbaum and G. Aeppli, Eur. Phys. J. Special Topics 224, 25 (2015) Traditional simulated annealing uses thermal fluctuations for convergence in optimization problems. Quantum tunneling provides a different mechanism for moving between states, with the potential for reduced time scales and different outcomes. Thermal and quan- tum annealing are compared in two concentration regimes of a model disordered magnet, where the effects of quantum mechanics can be tuned both by varying an applied magnetic field and by controlling the strength of thermal coupling between the magnet and an external heat bath. The results indicate that quantum annealing hastens convergence to the final state, and that the quantum character of the final state can be engineered thermodynamically. |
Department of quantum mesoscopics: seminar, Friday, April 8, 2016, ITF, 3:00 pm K. S. Tikhonov What is the computational value of finite range tunneling? Referativnyi doklad po rabote V. S. Denchev et al (Google Inc.), arxiv.org/1512.02206 Quantum annealing (QA) has been proposed as a quantum enhanced optimization heuristic exploiting tunneling. Here, we demonstrate how finite range tunneling can provide considerable computational advantage. For a crafted problem designed to have tall and narrow energy barriers separating local minima, the D-Wave 2X quantum annealer achieves significant runtime advantages relative to Simulated Annealing (SA). For instances with 945 variables, this results in a time-to-99%-success-probability that is ∼108 times faster than SA running on a single processor core. We also compared physical QA with Quantum Monte Carlo (QMC), an algorithm that emulates quantum tunneling on classical processors. We observe a substantial constant overhead against physical QA: D-Wave 2X again runs up to ∼108 times faster than an optimized implementation of QMC on a single core. We note that there exist heuristic classical algorithms that can solve most instances of Chimera structured problems in a timescale comparable to the D-Wave 2X. However, we believe that such solvers will become ineffective for the next generation of annealers currently being designed. To investigate whether finite range tunneling will also confer an advantage for problems of practical interest, we conduct numerical studies on binary optimization problems that cannot yet be represented on quantum hardware. For random instances of the number partitioning problem, we find numerically that QMC, as well as other algorithms designed to simulate QA, scale better than SA. We discuss the implications of these findings for the design of next generation quantum annealers. |
Department of quantum mesoscopics: seminar, Friday, March 25, 2016, ITF, 3:00 pm Lara Faoro (U Paris 6 & 7) Out-of-time-order correlators in solid state physics Out-of-time-order correlators introduced recently in the context of quantum gravity describe the delocalization of information in quantum systems. In classical chaotic systems, these correlators are known to grow exponentially with the Lyupanov exponent. I discuss the behavior of these correlators in canonical examples of solid state quantum chaotic systems: disordered electrons with and without phonon interaction. |
Department of quantum mesoscopics: seminar, Friday, March 11, 2016, ITF, 3:00 pm D. Shapiro, A. Shnirman and A. Mirlin Current-phase relation and h/e-periodic critical current of a chiral Josephson contact between 1D Majorana modes We explore a long Josephson contact transporting Cooper pairs between 1D charge-neutral chiral Majorana modes in the leads via charged Dirac chiral modes in the normal region. We investigate the regimes of transparent and tunnel junctions implemented in 3D topological insulator/superconductor/magnet hybrid structures. The setup acts as a SQUID controlled by the magnetic flux enclosed by the chiral loop of the normal region. This chirality leads to the fractional h/e-periodic pattern of critical current. The current-phase relation can have sawtooth-like shape with spikes at unusual even phases of 2\pi n. |
Department of quantum mesoscopics: seminar, Friday, November 6, 2015, ITF, 3:00 pm M. V. Feigel'man Level repulsion exponent β for Many-Body Localization Transitions and for Anderson Localization Transitions via Dyson Brownian Motion Referativnyi doklad po rabote Cecile Monthus, arxiv:1510.08322. |
Department of quantum mesoscopics: seminar, Friday, October 16, 2015, ITF, 3:00 pm Sergei Mironov (MFTI) Dzhozefsonovskii transport cherez nanoprovoloki: mnogokanal'naya interferentsiya i magnitnye ostsillyatsii V rabote teoreticheski pokazano, chto kriticheskii tok dzhozefsonovskogo kontakta, soderzhashchego nanoprovoloku s dvumya provodyashchimi kanalami, ispytyvaet mnogoperiodicheskie magnitnye ostsillyatsii. Mnogoperiodichnost' voznikaet iz-za kvantovomekhanicheskoi interferentsii mezhdu kanalami, na kotoruyu sushchestvennoe vliyanie okazyvayut sil'nye spin-orbital'noe i zeemanovskoe vzaimodeistviya. Rassmotrennaya minimal'naya dvukhkanal'naya model' pozvolyaet ob'yasnit' slozhnye interferentsionnye yavleniya, obnaruzhennye v eksperimentakh po izmereniyu dzhozefsonovskogo transporta cherez nanoprovoloki vismuta. |
Department of quantum mesoscopics: seminar, Friday, October 2, 2015, ITF, 3:00 pm K. Tikhonov Kagome chiral spin liquid as a gauged U(1) symmetry protected topological phase Referativnyi doklad po rabote Y.-C. He, S. Bhattacharjee, F. Pollmann, R. Moessner, arXiv:1509.03070 |
Department of quantum mesoscopics: seminar, Friday, September 25, 2015, ITF, 3:00 pm I. Burmistrov Tunneling into the localized phase near Anderson transitions |
Department of quantum mesoscopics: seminar, Friday, September 18, 2015, ITF, 3:00 pm E. Repin Topologicheskii Kondo izolyator Referativnyi doklad pro vozmozhnuyu realizatsiyu topologicheskogo izolyatora v sil'nokorrelirovannoi elektronnoi sisteme. Teoreticheskoe predskazanie i eksperimental'nye svidetel'stva v materiale SmB_6. [1] M. Dzero, K. Sun, V. Galitski, P. Coleman, PRL 104, 106408 (2010). |
Department of quantum mesoscopics: seminar, Friday, May 8, 2015, ITF, 3:00 pm E.S. Tikhonov (IFTT RAN, dokladchik), D.V. Shovkun, D.Kh. Kvon, N.N. Mikhailov, S.A. Dvoretskii, V.S. Khrapai Drobovoi shum kraevogo transporta v kvantovoi yame HgTe s invertirovannoi zonnoi strukturoi My izuchaem tokovyi shum v CdHgTe/HgTe/CdHgTe kvantovoi yame s invertirovannoi zonnoi strukturoi v rezhime neuporyadochennogo kraevogo transporta. V soglasii s predydushchimi eksperimentami soprotivlenie kraya sushchestvenno prevoskhodit h/e2 i slabo zavisit ot temperatury. Drobovoi shum v rezhime kraevogo transporta znachitel'no podavlen po sravneniyu s puassonovskim znacheniem i kharakterizuetsya faktorom Fano v diapazone 0.1 < F < 0.3 dlya razlichnykh obraztsov i znachenii zatvornogo napryazheniya. S uchetom togo, chto dlina kraya men'she ballisticheskoi dliny sboya fazy, eti nablyudeniya isklyuchayut vozmozhnost' odnomernogo gelikal'nogo kraevogo transporta v nashikh obraztsakh. Rezul'taty eksperimenta kachestvenno mozhno ob'yasnit' v modeli neuporyadochennogo mnogokanal'nogo kvazi-odnomernogo transporta vdol' kraya. |
Department of quantum mesoscopics: seminar, Friday, April 17, 2015, ITF, 3:00 pm Igor' Zagorodnev (MFTI/IRE RAN) Rezonansnoe rasseyanie elektronov v grafene na kruglom nanootverstii Vychisleno transportnoe sechenie rasseyaniya elektronov v grafene na kruglom otverstii (ili defekte). Predpolagaetsya, chto na krayu otverstiya mogut sushchestvovat' kvazistatsionarnye kraevye (tammovskie) sostoyaniya, kotorye privodyat k pikam v sechenii rasseyaniya, kotorye mogli nablyudat'sya v transportnykh eksperimentakh [Yu.I. Latyshev i dr., Pis'ma v ZhETF 98, 242 (2013), Yu.I. Latyshev et al., Scientific Reports 4, 7578 (2014)]. Obsuzhdaetsya uchet neodnorodnosti kraya, a takzhe zaryazhennosti nanootverstiya (defekta), chto privodit k razmytiyu i smeshcheniyu pikov. |
Department of quantum mesoscopics: seminar, Friday, January 9, 2015, ITF, 11:00 am Yasuhiro Asano (Hokkaido University, Japan) Odd-frequency Cooper Pairs The concept of the odd-frequency Cooper pairs was first proposed by Berezinskii in 1974 to describe superfluidity of 3He [1]. Although the odd-frequency superconductivity has never been confirmed in any materials, the odd-frequency pairs appear as the subdominant pairing correlation in various proximity structures such as superconductor / ferromagnet (SF) junctions [2] and normal-metal / superconductor (NS) junctions with unconventional pairing symmetry [3]. In the presentation, we explain what the odd-frequency pairs are, how they appear in such proximity structure, how to detect them, and how they are different from usual even-frequency pairs in the bulk. We first discuss the enhancement of the quasiparticle density of states at the zero-energy [2,4-5] and its influence on the low-energy electric transport [6]. Next we show the paramagnetic property of odd-frequency pairs [7-10] which can be confirmed in the surface impedance measurement at low temperature [11]. We also discuss a relation to the Majorana physics [12-13]. Finally we explain why such unusual pairs appear in inhomogeneous superconducting systems [14]. [1] V. L. Berezinskii, JETP Lett. 20, 287 (1974). [2] F. S. Bergeret, A. F. Volkov, and K. B. Efetov, Phys. Rev. Lett. 86, 4096 (2001) [3] Y. Tanaka and A. A. Golubov, Phys. Rev. Lett. 98, 037003 (2007). [4] Y. Asano, Y. Tanaka, and A. A. Golubov, Phys. Rev. Lett.98, 107002 (2007). [5] T. Kontos, et. al. Phys. Rev. Let. 86, 304 (2001). [6] Y. Asano, et. al., Phys. Rev. Lett. 99, 067005 (2007). [7] H. Walter, et. al., Phys. Rev. Lett. 80, 3598 (1998). [8] S. Higashitani, J. phys. soc. Jpn., 66, 2556 (1997). [9] S.-I. Suzuki and Y. Asano, Phys. Rev. B 89, 184508 (2014). [10] Y. Tanaka, et. al., Phys. Rev. B 72, 140503(R) (2005). [11] Y. Asano, et. al,, Phys. Rev. Lett. 107, 087001 (2011). [12] Y. Asano and Y. Tanaka, Phys. Rev. B 87, 104513 (2013). [13] S. Ikegaya, Y. Asano, and Y. Tanaka, arXiv: 1411.3438 [14] Y. Asano, Y. V. Fominov, Y. Tanaka, Phys. Rev. B 90, 094512 (2014). |
Department of quantum mesoscopics: seminar, Friday, December 19, 2014, ITF, 3:00 pm E. J. Koenig (Karlsruhe) Half-integer quantum Hall effect of disordered Dirac fermions at a topological insulator surface The unconventional (half-integer) quantum Hall effect for a single species of Dirac fermions is analyzed. In the introduction I will discuss experimental measurements of the half-integer Hall conductance g_{xy} of topological insulator surface states and unveil its field theoretical origin. For the calculation of the conductivity tensor, the following two step procedure is applied. In the first step, semiclassical transport coefficients are derived in the case of both orbital and Zeeman coupling to an external magnetic field. In this context, I plan to give a pedagogic review of the modified Boltzmann transport theory for the anomalous Hall effect. The semiclassical conductivity tensor serves as input parameters for the second step: It consists in the renormalization group treatment of the appropriately modified non-linear sigma model and thus accounts for localization effects. The resulting phase diagram (levitation scenario) will also be discussed in this context. If time permits, I will further explain how to reconcile Laughlin's flux insertion argument with half-integer Hall conductance and/or present the calculation of the current density beyond linear response in the limit of smooth scalar potential. |
Department of quantum mesoscopics: seminar, Friday, December 12, 2014, ITF, 3:00 pm I. V. Zagorodnev (IRE RAN) O vozmozhnykh spektrakh poverkhnostnykh sostoyanii v 2D i 3D topologicheskikh izolyatorakh Obychno schitaetsya, chto v topologicheskikh izolyatorakh (TI) spektr poverkhnostnykh sostoyanii imeet besshchelevoi lineinyi (ul'trarelyativistskii) spektr v tsentre zony Brillyuena. Takoi spektr deistvitel'no poluchaetsya v prosteishikh modelyakh pri ispol'zovanii “otkrytykh granichnykh uslovii” (open boundary conditions) [X.-L. Qi, S.-C. Zhang, Rev. Mod. Phys. 83, 1057 (2011)], t.e. granichnykh uslovii zanulyayushchikh volnovuyu funktsiyu na granitse. Odnako, izvestno, chto effektivnaya volnovaya funktsiya, opisyvayushchaya elektrony v kristalle, ne obyazana zanulyat'sya na granitse [E.L. Ivchenko “Optical Spectrosopy of Semiconductor Nanostructires”, Alpha Science, Harrow, UK (2005) i ssylki v nei]. Teoriya TI, a tochnee “printsip sootvetstviya granitsa-ob'em” (bulk boundary correspondence) predskazyvaet nalichie kraevykh sostoyanii v ob'emnoi shcheli, no ne sam spektr, kotoryi dolzhen zaviset' ot svoistv i mikrostruktury poverkhnosti, chto ne uchityvaetsya otkrytymi granichnymi usloviyami. V nashei rabote arXiv:1407.0945 byli proanalizirovany vozmozhnye granichnye usloviya v 2D TI na osnove kvantovykh yam CdHgTe i v 3D TI Bi2Se3. Pokazano, chto poverkhnostnye sostoyaniya mogut imet' sushchestvenno ne lineinyi spektr ili vovse otsutstvovat' v tsentre zony Brillyuena. |
Department of quantum mesoscopics: seminar, Friday, December 5, 2014, ITF, 3:00 pm V. V. Sivak, A. S. Ioselevich "Polzuchaya" provodimost' i relaksatsiya v sisteme metallicheskikh granul My rassmatrivaem sistemu provodnikov, pomeshchennykh v dielektricheskuyu matritsu. Matritsa ne predpolagaetsya sovershenno zhestkoi (naprimer, eto mozhet byt' zhidkost'), poetomu tolshchiny dielektricheskikh zazorov mezhdu provodnikami fluktuiruyut vo vremeni i inogda provodniki mogut soprikasat'sya. V takie momenty voznikaet "proboi" i zaryad legko peretekaet mezhdu paroi soprikosnuvshikhsya provodnikov. Protsess perenosa zaryada za schet proboev, voznikayushchikh v sluchainye momenty v sluchainykh mestakh, my nazvali polzuchei provodimost'yu. My rassmatrivaem kak trekhmernye, tak i nizkorazmernye massivy provodnikov i issleduem rastekanie zaryada, pervonachal'no sosredotochennogo na odnom provodnike, provodimost' na postoyannom toke, fluktuatsii zaryadov na provodnikakh i ikh prostranstvenno-vremennuyu korrelyatsiyu. |
Department of quantum mesoscopics: seminar, Friday, November 28, 2014, ITF, 3:00 pm Lev Ioffe Nonergodicity and many body localization in Josephson junction chains |
Department of quantum mesoscopics: seminar, Friday, November 21, 2014, Landau ITP, 3:00 pm Daniil Antonenko Kvantovyi effekt Kholla v grafene Obzor rabot Nature 505, 528 (2014) Tunable symmetry breaking and helical edge transport in a graphene quantum spin Hall state, A F Young, J D Sanchez-Yamagishi, B Hunt, S H Choi, K Watanabe, T Taniguchi, R C Ashoori and P Jarlillo-Herrero, Nat Phys 8, 550 (2012) Spin and valley quantum Hall ferromagnetism in graphene, A F Young, C R Dean, L Wang, H Ren, P Cadden-Zimansky, K Watanabe, T Taniguchi, J Hone, K L Shepard and P Kim |
Department of quantum mesoscopics: seminar, Thursday, November 20, 2014, Kaptiza Institute, 11:30 am K. S. Tikhonov Obzor nedavnikh rabot po mnogochastichnoi lokalizatsii |
Department of quantum mesoscopics: seminar, Friday, November 14, 2014, Landau ITP, 3:00 pm Eslam Khalaf (MPI FKF Stuttgart) Localization at the edge of a 2D topological insulator We study transport via edge modes of a 2D topological insulator. Topological protection prevents complete localization of the edge states; however, quantum interference effects are still relevant for the transport properties at finite length scales. We mainly focus on the two most experimentally relevant cases: (i) a junction between two quantum Hall insulators with different filling factors and hence an imbalance in the number of right- and left-propagating modes (symmetry class A) and (ii) a relatively thick HgTe quantum well in the insulating state with an arbitrary number of edge modes (symmetry class AII). We derive the distribution of transmission probabilities as a function of the distance between leads. This allows us to demonstrate topological effects in the average conductance and the shot noise of the setup. We also consider mesoscopic fluctuations and compute the variance of conductance. This quantity is strongly influenced by topology in the quantum Hall case. All the calculations are carried out assuming localization effects are weak, i.e., in the short length limit. Technically, this amounts to studying 1D non-linear sigma model with a proper topological term and source fields on the semiclassical level. Remarkably, the semiclassical limit of the 1D sigma model can be exactly mapped onto a fully quantum 0D sigma model of a different symmetry class. This allows us to identify the distribution of transmission probabilities with the spectrum of a certain random matrix. |
Department of quantum mesoscopics: seminar, Friday, October 24, 2014, Landau ITP, 3:00 pm Tat'yana Golikova (IFTT) Effekt blizosti i kogerentnye yavleniya v gibridnykh strukturakh sverkhprovodnik-normal'nyi metall-ferromagnetik Rabota posvyashchena izgotovleniyu submikronnykh planarnykh S-N-S dzhozefsonovskikh kontaktov, planarnykh gibridnykh struktur na osnove sverkhprovodnika, normal'nogo metalla i ferromagnetika, eksperimental'nomu issledovaniyu osobennostei effekta blizosti i sverkhprovodyashchego transporta cherez takie struktury, realizatsii S-(N/F)-S - dzhozefsonovskogo kontakta s ferromagnitnym monodomennym podsloem (F), issledovaniyu vliyaniya ferromagnitnogo podsloya na parnyi i kvazichastichnyi transport cherez dzhozefsonovskii S-(N/F)-S kontakt, izucheniyu nelokal'nykh neravnovesnykh effektov v mnogoterminal'nykh SNS strukturakh, svyazannykh s inzhektsiei kvazichastits v odin iz beregov dzhozefsonovskogo S-N-S kontakta. |
Department of quantum mesoscopics: seminar, Friday, October 10, 2014, Landau ITP, 3:00 pm Igor' Gornyi TBA |
Department of quantum mesoscopics: seminar, Friday, September 26, 2014, Landau ITP, 3:00 pm S. V. Zaitsev-Zotov (IRE RAN) Vliyanie strukturnykh defektov i atomnykh stupenei na lokal'nuyu plotnost' sostoyanii atomno-chistoi poverkhnosti topologicheskogo izolyatora Bi2Se3 Predstavleny rezul'taty issledovaniya atomno-chistoi poverkhnosti topologicheskogo izolyatora Bi2Se3 metodami sverkhvysokovakuumnoi nizkotemperaturnoi skaniruyushchei tunnel'noi mikroskopii (STM) i spektroskopii (STS). Obnaruzheny defekty glubina zaleganiya i ozhidaemyi zaryad kotorykh sootvetstvuet r-tipu provodimosti ob'ema kristalla. Znak termo-eds takzhe sootvetstvuet r-tipu provodimosti. Rezul'taty issledovanii metodami tunnel'noi spektroskopii pokazyvayut, chto uroven' khimicheskogo potentsiala nakhoditsya vnutri zapreshchennoi zony ob'ema. Obnaruzheno izmenenie lokal'noi plotnosti sostoyanii vblizi kraya pyatisloinoi stupeni, kotoroe sootvetstvuet sdvigu polozheniya vershiny dirakovskogo konusa otnositel'no ob'emnoi zony ili zhe takzhe sdvigu khimicheskogo potentsiala vblizi kraya stupeni. po rabote A.Yu. Dmitriev et al., http://arxiv.org/abs/1408.4991 |
Department of quantum mesoscopics: seminar, Friday, September 19, 2014, Landau ITP, 3:00 pm M. V. Feigel'man Raznoe |
Department of quantum mesoscopics: seminar, Friday, September 12, 2014, Landau ITP, 3:00 pm Artem Sboychakov (ITAE RAS, Moscow) AA-stacked bilayer graphene in an applied electric field: Tunable antiferromagnetism and coexisting exciton order parameter We study electronic properties of AA-stacked bilayer graphene. In the single-particle approximation such a system has one electron band and one hole band crossing the Fermi level. If the bilayer is undoped, the Fermi surfaces of these bands coincide. Such a band structure is unstable with respect to a set of spontaneous symmetry violations. Specifically, strong on-site Coulomb repulsion stabilizes antiferromagnetic order. At small doping and low temperatures, the homogeneous phase is unstable and experiences phase separation into an undoped antiferromagnetic insulator and a metal. The metallic phase can be either antiferromagnetic (commensurate or incommensurate) or paramagnetic depending on the system parameters. We derive the phase diagram of the system on the doping-temperature plane and find that under certain conditions, the transition from the paramagnetic to the antiferromagnetic phase may demonstrate reentrance. The application of the transverse voltage induces the exciton order parameter coexisting with antiferromagnetism. The value of this second order parameter is proportional to the biased voltage and the value of the nearest- neighbor inter-plane Coulomb repulsion. |
Department of quantum mesoscopics: seminar, Monday, July 28, 2014, Kapitza Institute, 10:00 am E. Sukhorukov (University of Geneve) Fermi Edge Singularity in Chiral One-dimensional Systems far from Equilibrium We study the effects of strong coupling of a localized state charge to one-dimensional electronic channels out of equilibrium. While the state of this charge and the coupling strength determine the scattering phase shifts in the channels, the non-equilibrium partitioning noise induces the tunneling transitions to the localized state. The strong coupling leads to a non-perturbative backaction effect which is manifested in the orthogonality catastrophe and the Fermi edge singularity in the transition rates. The non-Gaussian component of noise brakes the charge symmetry, shifting the position of the tunneling resonance depending on the sign of the dissipative current and the transparency of the noise emitting partitioning quantum point contact. |
Department of quantum mesoscopics: seminar, Friday, July 4, 2014, ITF, 11:00 am Y. Tanaka (Nagoya University, Japan) Theory of topological superconductivity |
Department of quantum mesoscopics: seminar, Friday, April 18, 2014, Landau ITP, 3:00 pm V. V. Pogosov (ITPE) Veroyatnostnyi podkhod k resheniyu uravnenii Richardsona-Godena (anzatsa Bete) Predlozhen novyi pokhod k resheniyu uravnenii Richardsona-Godena, kotorye opredelyayut sobstvennye sostoyaniya gamil'toniana teorii Bardina-Kupera-Shriffera (BKSh). Vmesto neposredstvennogo resheniya etikh uravnenii mozhno pereiti k veroyatnostnomu predstavleniyu i zatem rekonstruirovat' polozheniya kornei etikh uravnenii na kompleksnoi ploskosti, ispol'zuya metody integrirovaniya. Pri etom voznikayut integraly sel'bergovskogo tipa, figuriruyushchie v konformnoi teorii polya i teorii sluchainykh matrits. V rabote provedeny analiticheskie raschety dlya nizkoenergeticheskoi chasti spektra sistemy v termodinamicheskom predele, dlya kotorogo podtverzhdeno soglasie so srednepolevymi predskazaniyami BKSh. Takzhe predstavleny nekotorye rezul'taty dlya sistem proizvol'nogo razmera, dlya chego byla privlechena ideya o simmetrii mezhdu parami elektronov i parami dyrok. Veroyatnostnyi podkhod mozhet byt' polezen i dlya resheniya drugikh tipov uravnenii Bete. |
Department of quantum mesoscopics: seminar, Friday, April 11, 2014, Landau ITP, 3:00 pm E. V. Devyatov (IFTT) Dinamika namagnichennosti, vyzvannaya protekayushchim tokom, na granitse dvumernoi elektronnoi sistemy s sil'nym spin-orbital'nym vzaimodeistviem My eksperimental'no issledovali transport cherez interfeis mezhdu ferromagnetikom (permalloi) i kraem dvumernoi elektronnoi sistemy s sil'nym spin-orbital'nym vzaimodeistviem tipa Rashby. My obnaruzhili sil'no nelineinye transportnye kharakteristiki v oblasti malykh tokov pri millikel'vinovykh temperaturakh. Obnaruzhennaya nelineinost' polnost'yu podavlyaetsya pri dostizhenii nekotorykh znachenii temperatury, magnitnogo polya ili toka cherez interfeis. My interpretiruem dannoe povedenie kak rezul'tat spinovoi akkumulyatsii vblizi interfeisa i ee absorbtsii, vyzvannoi protekayushchim tokom (magnetization torque). |
Department of quantum mesoscopics: seminar, Friday, April 4, 2014, Landau ITP, 3:00 pm Dmitry Bagrets (Institute for Theoretical Physics, University of Cologne) Quantum criticality in quasi one-dimensional topological nanowires Using the combination of analytical and numerical techniques we develop the theory of quantum criticality in disordered topological multi-channel nanowires of symmetry classes AIII and BDI [1]. The minimal representative phase portrait is characterized by two parameters $(\mu, w)$, where $\mu$ is the external control parameter (e.g. the chemical potential) and $w$ is the disorder strength. With the increase of $w$ at a fixed value of $\mu$ the wires generically undergo a sequence of topological phase transitions before the asymptotic state of a trivial Anderson insulator is reached. The universal description of the systems is given in terms of two parameters $(g,\chi)$, where $g$ is conductance and $\chi$ is a topological angle. Contour lines of half-integer valued $\chi$ in $(\mu, w)$-parameter space define phase boundaries between distinct topological sectors. Upon increasing the length of the wire, the pair $(g, \chi)$ exhibits flow similar to the celebrated two parameter flow describing the class A quantum Hall insulator. However, unlike the quantum Hall system, an exact analytical description of the entire phase diagram can be given. We corroborate the quantitative validity of our theory by comparison to numerical transfer matrix computations. [1] A. Altland, D. Bagrets, L. Fritz, A. Kamenev, H. Schmiedt, arXiv:1402.1738 |
Department of quantum mesoscopics: seminar, Friday, March 28, 2014, Landau ITP, 2:00 pm P. Grigor'ev Magnitosoprotivlenie sloistykh metallov Budet dana klassifikatsiya razlichnykh predel'nykh sluchaev, svyazannykh s sootnosheniyami mezhdu integralom mezhsloevogo pereskoka, rasstoyaniem, i shirinoi urovnei Landau. V kazhdom predel'nom sluchae budut ukazany metod vychisleniya mezhsloevoi provodimosti v sil'no anizotropnykh kvazidvumernykh metallakh, oblast' primenimosti etogo metoda, i glavnye rezul'taty etikh raschetov. [*] P. D. Grigoriev, "Longitudinal interlayer magnetoresistance in quasi-two-dimensional metals", Phys. Rev. B 88, 054415 (2013). a takzhe
|
Department of quantum mesoscopics: seminar, Friday, January 31, 2014, Landau ITP, 3:00 pm S. I. Dorozhkin (IFTT) Flips of electric field in microwave-induced states with spontaneously broken symmetry We present new results on the bistability effect recently observed [Dorozhkin et al., Nature Physics 7, 336 (2011)] in two-dimensional electron systems subjected to the microwave radiation. The effect appears as switching between two states with different electric potential distribution across a sample. Our results here imply that the main difference between these two states is an opposite direction of a long lengthscale electric field which arises spontaneously under conditions when the observable magnetoresistance tends to zero. Although a possibility of the field reversal is an inherent property of states with spontaneously broken symmetry, so far such effect was never observed under stationary external conditions. |
Department of quantum mesoscopics: seminar, Friday, December 20, 2013, Landau ITP, 3:00 pm Vasilii Vadimov (IFM RAN, Nizhnii Novgorod) Generatsiya domennykh stenok v p_x+ip_y sverkhprovodnikakh pri pomoshchi perekhodov, narushayushchikh Z_2 simmetriyu V rabote byli issledovany sverkhprovodniki, obladayushchie tripletnym p_x+ip_y tipom sparivaniya, obladayushchie dvukratno vyrozhdennym osnovnym sostoyaniem. Bylo pokazano nalichie fazovogo perekhoda pod deistviem vneshnego magnitnogo polya ili transportnogo toka, snimayushchego dvukratnoe vyrozhdenie i vosstanavlivayushchego Z_2 simmetriyu. Takoi perekhod daet vozmozhnost' dlya upravlyaemoi generatsii domennykh stenok, svyazannykh s narushennoi Z_2 simmetriei osnovnogo sostoyaniya, po mekhanizmu Kibbla-Zureka. Predlozhennyi sposob generatsii domennykh stenok mozhet byt' realizovan v takikh ekzoticheskikh sverkhprovodnikakh kak Sr2RuO4 i v nekotorykh soedineniyakh s tyazhelymi fermionami. po rabote V. Vadimov, M. Silaev, Phys. Rev. Lett. 111, 177001 (2013) |
Department of quantum mesoscopics: seminar, Friday, December 13, 2013, Landau ITP, 3:00 pm P. A. Ioselevich Navedennaya sverkhprovodimost' na krayu sistemy v rezhime kvantovogo spinovogo effekta Kholla (referativnyi doklad) Budet rasskazano o nedavnikh izmereniyakh sverkhtoka v SNS-kontakte v geterostrukture HgTe/HgCdTe v rezhime kvantovogo spinovogo effekta Kholla [1]. Maksimal'nyi sverkhtok v sisteme izmeren kak funktsiya magnitnogo polya, napravlennogo perpendikulyarno dvumernomu obraztsu, a takzhe zavtornogo napryazheniya, reguliruyushchego plotnost' nositelei v ob'eme. V rezhime, kogda ob'emnye nositeli predpolozhitel'no otsutstvuyut, zavisimost' I(B) imeet priblizitel'no sinusoidal'nyi vid, chto sootvetstvuet sverkhtoku, tekushchemu tol'ko po krayam obraztsa. Period ostsillyatsii sootvetstvuet kvantu potoka Phi_0 cherez kontakt, a amplituda medlenno zatukhaet s rostom magnitnogo polya. Budut obsuzhdeny vozmozhnye prichiny zatukhaniya sverkhtoka, perenosimogo gelikoidal'nymi kraevymi modami. [1] Molenkamp, Yacoby et al., http://arxiv.org/abs/1312.2559 |
Department of quantum mesoscopics: seminar, Friday, November 29, 2013, Landau ITP, 3:00 pm P. Aseev (IRE RAN) Spinovyi tok v topologicheskom izolyatore s ob'emnymi kontaktami Rassmatrivaetsya provodyashchee sostoyanie v 2D i 3D topologicheskom izolyatore (TI), tunnel'nym obrazom soedinennom s elektrodami iz normal'nogo metalla. Pokazano, chto kontakty, igraya rol' termostata, vyzyvayut zatukhanie i privodyat k relaksatsii elektronov v TI. Predlozhena prostaya struktura na osnove TI s tunnel'nymi kontaktami, sozdayushchaya chisto spinovyi tok vo vneshnei tsepi. Issleduetsya zavisimost' elektricheskogo i spinovogo toka vo vneshnei tsepi ot sootnosheniya mezhdu kharakternymi dlinami: dlinoi zatukhaniya iz-za tunnelirovaniya, dlinoi kontaktov i, v sluchae 3D TI, dlinoi svobodnogo probega i relaksatsii spina, vyzvannoi rasseyaniem impul'sa na primesyakh. |
Department of quantum mesoscopics: seminar, Friday, November 22, 2013, Landau ITP, 3:00 pm A. Kamenev (University of Minnesota) Statistical mechanics of Coulomb gases as quantum theory on Riemann surfaces A number of physical problems may be formulated in terms of non-Hermitian quantum theories. A notable example is provided by mapping of 1D Coulomb gases onto an effective non-Hermitian Quantum Mechanics. Employing methods from algebraic topology we describe a non-perturbative method of instanton calculus for non-Hermitian Hamiltonians. Treating momentum and coordinate as complex variables yields Riemann surfaces of complex energy. The classical and instanton actions are given by the periods of this surface. We demonstrate the accuracy of this analytic procedure in comparison with numerical simulations for a class of periodic non-Hermitian Hamiltonians, as well as the validity of the Bohr-Sommerfeld quantization and Gamow’s formula in these cases. |
Department of quantum mesoscopics: seminar, Friday, September 20, 2013, Landau ITP, 3:00 pm M. Serbin (MIT) New Dirac points and multiple Landau level crossings in biased trilayer graphene Recently a new high-mobility Dirac material, trilayer graphene, was realized experimentally. The band structure of ABA-stacked trilayer graphene consists of a monolayer-like and a bilayer-like pair of bands. Here we study electronic properties of ABA-stacked trilayer graphene biased by a perpendicular electric field. We find that the combination of the bias and trigonal warping gives rise to a set of new Dirac points: In each valley, seven species of Dirac fermions with small masses of order of a few meV emerge. The positions and masses of the emergent Dirac fermions are tunable by bias, and one group of Dirac fermions becomes massless at a certain bias value. Further, we analyze the evolution of the Landau level spectrum as a function of bias. We develop a theoretical model and argue that, in contrast to monolayer and bilayer graphene, the Landau level splittings and quantum Hall phase transitions observed in a recent experiment can be understood within a single-particle picture, but imply the presence of a charge density imbalance between the inner and outer layers of TLG, even at charge neutrality and zero transverse electric field. Our results indicate the importance of a previously unaccounted band structure parameter. We show that the pattern of Landau level crossings is very sensitive to certain band structure parameters, and can therefore provide a useful tool for determining their precise values. |
Department of quantum mesoscopics: seminar, Friday, September 6, 2013, Landau ITP, 3:00 pm I. V. Gornyi (Karlsruhe and Ioffe PhysTech) Quantum Hall criticality and localization in graphene with short-range impurities at the Dirac point Strong impurities crucially affect the spectral and transport properties of graphene near the Dirac point creating the "mid-gap" states. We first consider the ultimate case of very strong on-site potential impurities that are equivalent to vacancies in the lattice. Vacancies in the honeycomb lattice possess two important properties: (i) they preserve the chiral symmetry of the model and (ii) they scatter resonantly at zero energy (Dirac point). We study the density of states in graphene with sublattice imbalance [1]: we assume that the concentration of vacancies is different in the two sublattices. The imbalance leads to a finite concentration of zero modes of the tight-binding Hamiltonian. We derive the non-linear sigma model for the chiral system with imbalance. Semiclassical density of states acquires a finite gap around the Dirac point with the delta-function peak exactly in the center of the gap. Finite density of zero modes results in the additional term in the sigma-model action. The perturbative renormalization group analysis of this theory yields corrections to the density of states above the gap. In order to obtain a finite density of states below the semiclassical gap, we include non- perturbative contributions to the partition function due to instanton configurations of the field. Further, we explore the longitudinal conductivity of graphene at the Dirac point in strong magnetic field with two types of short-range scatterers of a finite strength: adatoms that mix the valleys and "scalar" impurities that do not mix them [2]. A scattering theory for the Dirac equation is employed to express the conductance of a graphene sample at charge neutrality as a function of impurity coordinates; an averaging over positions of impurities is then performed numerically. The conductivity is equal to the ballistic value for each disorder realization, provided the number of flux quanta considerably exceeds the number of impurities. For weaker fields, the conductivity in the presence of scalar impurities scales to the quantum-Hall critical point at half filling or to zero away from half filling due to the onset of Anderson localization. For adatoms, the localization behavior is obtained also at half filling due to splitting of the critical energy by intervalley scattering. Our results reveal a complex scaling flow governed by fixed points of different symmetry classes. [1] E.J. Koenig, I.V. Protopopov, P.M. Ostrovsky, I.V. Gornyi, A.D. Mirlin, and M.A. Skvortsov, in preparation. [2] S. Gattenloehner, W.-R. Hannes, P. M. Ostrovsky, I. V. Gornyi, A. D. Mirlin, and M. Titov, "Quantum Hall criticality and localization in graphene with short-range impurities at the Dirac point", arXiv:1306.5686. |
Department of quantum mesoscopics: seminar, Friday, June 14, 2013, Landau ITP, 3:00 pm E. V. Devyatov (IFTT) Andreevskoe otrazhenie na krayu dvumernoi elektronnoi sistemy s sil'nym spin-orbital'nym vzaimodeistviem My eksperimental'no issledovali transportnye svoistva odinochnogo planarnogo kontakta mezhdu niobievym sverkhprovodyashchim elektrodom i kraem dvumernoi elektronnoi sistemy s sil'nym spin-orbital'nym vzaimodeistviem, realizovannoi v uzkoi InGaAs kvantovoi yame. My prodemonstrirovali podavlenie Andreevskogo otrazheniya v oblasti malykh napryazhenii, prilozhennykh k kontaktu, pri sverkhnizkikh temperaturakh (30 mK). Iz analiza temperaturnoi (do 1 K) zavisimosti i zavisimosti ot magnitnogo polya, orientirovannogo v ploskosti dvumernoi sistemy, my interpretiruem obnaruzhennoe podavlenie kak rezul'tat spin-orbital'nogo vzaimodeistviya. Tak zhe, pri opredelennom nabore parametrov, issleduemaya sistema demonstriruet priznaki realizatsii rezhima topologicheskoi sverkhprovodimosti. arXiv:1305.5685 |
Department of quantum mesoscopics: seminar, Friday, June 7, 2013, Landau ITP, 3:00 pm Oleg Lychkovskii (Lancaster Univ.) Dynamics of a mobile impurity in a one-dimensional quantum gas We consider a bath of fermions in one dimension at zero temperature, and an impurity particle immersed in this bath with some initial momentum. The following questions are addressed: How does the impurity momentum evolve? Does it relax to zero in the long run? |
Department of quantum mesoscopics: seminar, Friday, May 31, 2013, Landau ITP, 3:00 pm I.S. Burmistrov Mul'tifraktal'nost' vblizi perekhoda Andersona v prisutstvie kulonovskogo vzaimodeistviya V rabote izuchayutsya mezoskopicheskie fluktuatsii lokal'noi plotnosti sostoyanii okolo perekhoda metall-dielektrik v neuporyadochennoi vzaimodeistvuyushchei elektronnoi sisteme. Pokazano, chto mul'tifraktal'noe povedenie lokal'noi plotnosti sostoyanii vyzhivaet v prisutstvie kulonovskogo vzaimodeistviya. Dlya perekhoda metall-izolyator v prisutstvie kulonovskogo vzaimodeistviya v razmernosti 2+\epsilon vychislen spektr mul'tifraktal'nykh razmernostei, kotoryi okazyvaetsya drugim, chem v sluchae bez vzaimodeistviya. Doklad po rabote: I.S. Burmistrov, I.V. Gornyi, A.D. Mirlin, "Multifractality at Anderson transitions with Coulomb interaction", arxiv:1305.2888 |
Department of quantum mesoscopics: seminar, Friday, May 24, 2013, Landau ITP, 3:00 pm Pavel Shmakov (FTI im. A.F. Ioffe) Vysokotemperaturnyi effekt Aaronova-Boma v odnokanal'nykh kol'tsakh so slabym besporyadkom Teoreticheski izucheno vliyanie slabogo besporyadka na effekt Aaronova-Boma v odnokanal'nykh kvantovykh kol'tsakh s tunnel'nymi kontaktami. Temperatura predpolagaetsya mnogo bol'shei mezhurovnevogo rasstoyaniya v kol'tsakh. V otsutstvie besporyadka zavisimost' kondaktansa kolets ot magnitnogo potoka pri takikh temperaturakh imeet uzkie provaly (antirezonansy). Rassmotreno vliyanie razlichnykh tipov besporyadka na eti antirezonansy. Pokazano, chto korotkodeistvuyushchie primesi privodyat k ushireniyu antirezonansov, odnako ikh glubina ne menyaetsya v shirokom diapazone parametrov. Plavnyi besporyadok privodit k poyavleniyu novykh antirezonansov. Teoriya obobshchaetsya na sluchai, kogda v kol'tsakh pomimo primesei prisutstvuet spin-orbital'noe i zeemanovskoe vzaimodeistvie. http://arxiv.org/abs/1303.3486 |
Department of quantum mesoscopics: seminar, Friday, May 17, 2013, Landau ITP, 3:00 pm Dmitrii Lyubshin O statistike ekstremumov gaussovykh sluchainykh protsessov Planiruetsya (i) na dvukh primerakh iz stat. fiziki pokazat', kak mozhet vyglyadet' statistika minimumov gaussova sluchainogo protsessa; (ii) proyasnit' tekushchii matematicheskii status prostykh retseptov vychisleniya khvosta raspredeleniya minimuma; (iii) esli ostanetsya vremya, razobrat' vyvod polnoi statistiki dlya brounovskogo bluzhdaniya s kvadratichnym dreifom ("toy model") -- renormgruppu (Ma-Dasgupty) dlya sil'nogo besporyadka i ekvivalentnost' kvantovoi odnomernoi zadache Izinga v sluchainom poperechnom pole (chast' (iii) po Le Doussal, Monthus 2003). |
Department of quantum mesoscopics: seminar, Friday, April 19, 2013, Landau ITP, 3:00 pm Vladislav Kozii , Mikhail Skvortsov Mnogochastichnaya slabaya lokalizatsiya v kvantovoi tochke (predvaritel'noe soobshchenie) |
Department of quantum mesoscopics: seminar, Friday, April 12, 2013, Landau ITP, 3:00 pm I. S. Burmistrov Soobshchenie po tekushchim rabotam |
Department of quantum mesoscopics: seminar, Friday, April 5, 2013, Landau ITP, 3:00 pm M.V. Feigel'man Referat po rabote V. Kravtsova i dr. Interaction-driven localization transition at the Fermi-energy Metodom chislennogo analiza uravnenii na volnovye funktsii v priblizhenii Khatri-Foka pokazano, chto v standartnoi modeli Andersona na 3-kh mernoi reshetke s on-site disorder pri besporyadke W slegka men'she kriticheskogo znacheniya W_c=16.5, uchet kulonovskogo vzaimodeistviya privodit k fraktal'nomu povedeniyu volnovykh funktsii vblizi urovnya Fermi. Rezul'taty ukazyvayut na vozmozhnost' sushchestvovaniya tseloi promezhutochnoi "kriticheskoi fazy" v nekotoroi polose znachenii kulonovskoi konstanty vzaimodeistviya. |
Department of quantum mesoscopics: seminar, Friday, February 8, 2013, Landau ITP, 3:00 pm I. V. Kukushkin (IFTT) Magnitoplazmennye vozbuzhdeniya i perenormirovka skorosti elektronov i dyrok v grafene |
Department of quantum mesoscopics: seminar, Friday, November 23, 2012, Landau ITP, 3:00 pm Pavel Ioselevich Referativnyi doklad po eksperimental'noi rabote The fractional ac Josephson effect in a seminconductor- superconductor nanowire as a signature of Majorana particles L.Rokhinson et al Nature Physics, 8, 795 (2012) |
Department of quantum mesoscopics: seminar, Friday, November 2, 2012, Landau ITP, 3:00 pm E. V. Devyatov (IFTT) Energy spectrum reconstruction at the edge of a two-dimensional electron system with strong spin-orbit coupling We experimentally demonstrate the simultaneous reconstruction of the bulk and the edge energy spectra caused by strong spin-orbit interaction, at the two lowest filling factors ν=1 and ν=2 for InxGa1−xAs two-dimensional electron system with x=0.75. The observed reconstruction is of different character at these filling factors: It is characterized by zeroing of the energy gap at the levels crossing point at ν=2, while the reconstruction at ν=1 goes through the coexistence of two ν=1 quantum Hall phases with different spin projections. An analysis indicates a strong influence of many-body interaction on the reconstruction at ν=1. [A. Kononov, G. Biasiol, L. Sorba, and E. V. Deviatov, Phys. Rev. B 86, 125304 (2012)] |
Department of quantum mesoscopics: seminar, Thursday, June 7, 2012, Kapitza Institute, 11:30 am Elio Koenig (Karlsruhe Institute of Technology, Karlsruhe, Germany) Interaction and disorder effects in 3D topological insulator thin films It has been recently predicted that Coulomb interaction drives a surface of a 3D topological insulator into a critical state (Ostrovsky et al., PRL 105, 036803 (2010)). We employ the sigma-model formalism to investigate the effect of electron-electron interaction on the transport by surface states in topological insulator thin films. We take into account the interaction of electrons on different surfaces and also the top-bottom asymmetry of the film (different densities of states and strength of disorder on top/bottom surface). This asymmetry is naturally present in experiments where the electronic densities on the surfaces are controlled independently by means of electrostatic gates. The lack of symmetry between top and bottom surfaces is shown to have strong effect on the film conductivity. The interplay of weak antilocalization, Coulomb interaction within and between surfaces and topological protection leads to a rich flow diagram representing the low temperature behavior of the system. In particular, the intersurface interaction is found to evoke a non-monotonic temperature dependence of the conductuctivity and eventually drives the film into a metallic state. The connection with recent experiments on Bi_2Se_3 films is discussed. |
Department of quantum mesoscopics: seminar, Thursday, May 31, 2012, Kapitza Institute, 3:30 pm Igor' Mazin (Naval Research Laboratory, Washington, DC, USA) Neformal'noe obsuzhdenie polozheniya del s geksagonal'nymi iridatami i model'yu Geizenberg-Kitaeva |
Department of quantum mesoscopics: seminar, Friday, May 25, 2012, Landau ITP, 3:00 pm Alexander Altland, Yuval Gefen, Bernd Rosenow Incoherent scatterer in a Luttinger liquid: a new paradigmatic limit We address the problem of a Luttinger liquid with a scatterer that allows for both coherent and incoherent scattering channels. The asymptotic behavior at zero temperature is governed by a new stable fixed point: a Goldstone mode dominates the low energy dynamics, leading to a universal behavior. This limit is marked by equal probabilities for forward and backward scattering. Notwithstanding this non-trivial scattering pattern, we find that the shot noise as well as zero cross-current correlations vanish. We thus present a paradigmatic picture of an impurity in the Luttinger model, alternative to the Kane-Fisher picture. |
Department of quantum mesoscopics: seminar, Sunday, March 11, 2012, Landau ITP, 3:00 pm S. V. Iordanskii Provodimost' grafena i elektronno-dyrochnye pary |
Department of quantum mesoscopics: seminar, Friday, March 2, 2012, Landau ITP, 3:00 pm Elio König (Karlsruhe Institute of Technology) Metal-insulator transition in 2D random fermion systems of chiral symmetry classes Field-theoretical approach to Anderson localization in 2D disordered fermionic systems of chiral symmetry classes (BDI, AIII, CII) is developed. Important representatives of these symmetry classes are random hopping models on bipartite lattices at the band center. As was found by Gade and Wegner two decades ago within the sigma-model formalism, quantum interference effects in these classes are absent to all orders of perturbation theory. We demonstrate that the quantum localization effects emerge when the theory is treated non-perturbatively. Specifically, they are controlled by topological vortex-like excitations of the sigma models. We derive renormalization group equations including these non-perturbative contributions. Analyzing them, we find that the 2D disordered systems of chiral classes undergo a metal-insulator transition driven by topologically induced Anderson localization. We also show that the Wess-Zumino and Z_2 theta terms on surfaces of 3D topological insulators (in classes AIII and CII, respectively) overpower the vortex-induced localization. po rabote E.J. König, P. M. Ostrovsky, I. V. Protopopov, A. D. Mirlin, "Metal-insulator transition in 2D random fermion systems of chiral symmetry classes", arXiv:1201.6288v1 |
Department of quantum mesoscopics: seminar, Friday, January 13, 2012, Landau ITP, 4:00 pm Dmitrii Pikulin (Leiden) Tokovyi shum v dzhozefsonovskom kontakte s maioranovskimi fermionami |
Department of quantum mesoscopics: seminar, Friday, December 23, 2011, Landau ITP, 3:00 pm Jukka Pekola (Low Temperature Laboratory, Aalto University) Heat transport in mesoscopic (electron) systems at low temperatures |
Department of quantum mesoscopics: seminar, Friday, December 16, 2011, Landau ITP, 3:00 pm M. Feigel'man O vozniknovenii neobratimosti i teplovogo rezervuara v konechnoi kvantovoi sisteme Budet sdelan kratkii (minut na 30) kommentarii na temu, obsuzhdavshuyusya G. Lesovikom na ego doklade 15 dekabrya v IFP, s ispol'zovaniem resheniya (E. Cuevas, M. Feigel'man, L.Ioffe, M. Mezard) zadachi o reshetke spinov so sluchainym polem, rasskazannoi ranee (21.10.2011). |
Department of quantum mesoscopics: seminar, Friday, October 21, 2011, Landau ITP, 3:00 pm M. V. Feigel'man Statistika urovnei sistemy kvantovykh spinov 1/2 v sluchainom pole Budet predstavleno bolee podrobnoe izlozhenie rezul'tatov raboty E.Cuevas, M.Feigelman, L.Ioffe, M.Mezard "Level statistics of disordered spin-1/2 systems and its implications for materials with localized Cooper pairs", ob'yavlennykh v sentyabre na Uchenom Sovete ITF. |
Department of quantum mesoscopics: seminar, Friday, October 7, 2011, Landau ITP, 3:00 pm V.F. Gantmakher (IFTT) Otsutstvie perekhodov Andersona v materialakh s bol'shoi elektronnoi kontsentratsiei |
Department of quantum mesoscopics: seminar, Friday, June 17, 2011, Landau ITP, 3:00 pm M. V. Feigel'man Sil'no neuporyadochennye sverkhprovodniki i kvantovyi perekhod v izolyator: obzor postavlennykh, no nereshennykh zadach |
Department of quantum mesoscopics: seminar, Friday, May 27, 2011, Landau ITP, 3:00 pm Konstantin Tikhonov Deistvie Ginzburga-Landau dlya gryaznykh fluktuiruyushchikh sverkhprovodnikov. Obsuzhdaetsya obobshchenie fluktuatsionnogo deistviya Ginzburga-Landau v sigma-modeli Keldysha na sluchai proizvol'nykh temperatur i magnitnykh polei . Etot podkhod pozvolyaet vosproizvesti standartnye rezul'taty dlya fluktuatsionnykh popravok vo vsei oblasti vyshe perekhoda, a takzhe poluchit' novye rezul'taty dlya effekta Kholla, voznikayushchego za schet sverkhprovodyashchikh fluktuatsii. |
Department of quantum mesoscopics: seminar, Friday, May 20, 2011, Landau ITP, 3:00 pm Konstantin Tikhonov Obzornyi doklad po rabotam o Spin Seebeck Effect Obzornyi doklad po rabotam o Spin Seebeck Effect (otklik spinovogo
toka na gradient temperatury): |
Department of quantum mesoscopics: seminar, Friday, May 13, 2011, Landau ITP, 3:00 pm I. S. Burmistrov Referativnyi doklad po rabote Single-particle Green's function and interacting topological insulators [V. Gurarie, Phys. Rev B 83, 085426 (2011), arxiv: 1011.2273] |
Department of quantum mesoscopics: seminar, Friday, May 6, 2011, Landau ITP, 3:00 pm Yu. G. Makhlin Referativnyi doklad po rabote "Majorana path integral for nonequilibrium dynamics of two-level systems" [T.A. Sedrakyan, V.M. Galitski, Phys. Rev. B 83, 134303 (2011), arXiv:1012.2005] |
Department of quantum mesoscopics: seminar, Friday, April 8, 2011, Landau ITP, 3:00 pm I. Burmistrov i M. Feigel'man Soobshcheniya ob uslyshannom na konferentsii Rencontres des Moriond 13-19 marta |
Department of quantum mesoscopics: seminar, Friday, March 25, 2011, Landau ITP, 3:00 pm A. Shtyk (5 kurs) Referativnyi doklad po rabotam "Real-space observation of emergent magnetic monopoles and associated Dirac strings in artificial kagome spin ice" [E. Mengotti et al, Nature 7, 68 (2011)] "Creation and measurement of long-lived magnetic monopole currents in spin ice" [S. R. Giblin et al, Nature 7, 252 (2011)] |
Department of quantum mesoscopics: seminar, Friday, March 11, 2011, Landau ITP, 3:00 pm P.A. Ioselevich Referativnyi doklad po rabote Low-velocity anisotropic Dirac fermions on the side surface of topological insulators [Chang-Youn Moon et al, arXiv:1101.0210] |
Department of quantum mesoscopics: seminar, Friday, March 4, 2011, Landau ITP, 3:00 pm A.S. Ioselevich Referativnyi doklad po rabote Hydrodynamic description of transport in strongly correlated electron systems [A.V. Andreev, S.A. Kivelson, B. Spivak, arXiv:1011.3068] |
Department of quantum mesoscopics: seminar, Friday, February 18, 2011, Landau ITP, 3:00 pm E. V. Mozgunov (6 kurs) Referativnyi doklad po rabote "Interference under Tunnel Barrier and Esaki-Zener-type I-V Characteristic in Bilayer Graphene p-n Junctions" [R. Nandkishore, L. Levitov, arXiv:1101.0436] |
Department of quantum mesoscopics: seminar, Friday, February 11, 2011, Landau ITP, 3:00 pm Ya.V. Fominov Referativnyi doklad po rabote "Charge imbalance in superconductors in the low-temperature limit" [Hubler et al, Phys. Rev. B 81, 184524 (2010)] |
Department of quantum mesoscopics: seminar, Friday, January 28, 2011, Landau ITP, 3:00 pm P.A. Ioselevich Rasskaz o shkole po topologicheskim izolyatoram, proshedshei v Ierusalime |
Department of quantum mesoscopics: seminar, Friday, December 17, 2010, Landau ITP, 3:00 pm A.S. Ioselevich, Yu.G.Makhlin Soobshcheniya o zadachakh, nakhodyashchikhsya v rabote |
Department of quantum mesoscopics: seminar, Friday, December 3, 2010, Landau ITP, 3:00 pm Ya.I.Rodionov, I. S. Burmistrov Neravnovesnyi admittans odno-elektronnoi korobki v rezhime cil'noi kulonovskoi blokady Izucheny admittans i dissipatsiya energii v odno-elektronnoi korobke (malen'kii metallicheskii ostrovok, soedinennyi s rezervuarom tunnel'nym kontaktom; potentsial elektronov na ostrovke kontroliruetsya dopolnitel'nym zatvornym elektrodom) v neravnovesnom rezhime pri prilozhenii peremennogo zatvornogo napryazheniya v rezhime sil'noi kulonovskoi blokady. Vychislen admittans pri ne slishkom nizkoi effektivnoi temperature (energii) elektronov na ostrovke, kogda mozhno prenebrech' elektronnoi kogerentnost'yu, no neobkhodimo polnost'yu uchityvat' kvantovye fluktuatsii zaryada iz-za sil'nogo kulonovskogo vzaimodeistviya. Kak okazalos', dissipatsiya energii mozhet byt' vyrazhena cherez soprotivlenie zaryadovoi relaksatsii i perenormirovannuyu zaryadovuyu emkost' dazhe v neravnovesnykh usloviyakh. Povedenie admittansa kak funktsii vneshnei chastoty opredelyaetsya funktsiei raspredeleniya, otvechayushchei bozonnym kollektivnym vozbuzhdeniyam na ostrovke. Poetomu, mozhno ispol'zovat' admittans odno-elektronnoi korobki dlya izmereniya etoi bozonnoi funktsii raspredeleniya. |
Department of quantum mesoscopics: seminar, Friday, November 26, 2010, Landau ITP, 3:00 pm Azat Sharafutdinov (MFTI, 5 kurs) Tok kotunnelirovaniya cherez dvukh-urovnevuyu kvantovuyu tochku, soedinennuyu s magnitnymi kontaktami. Vliyanie obmennogo vzaimodeistviya Vychislen tok v rezhime ko-tunnelirovaniya cherez dvukhurovnevuyu kvantovuyu tochku slabo svyazannuyu s ferromagnitnymi kontaktami. Pokazano, chto zavisimost' differentsial'nogo kondaktansa ot prilozhennogo napryazheniya imeet vid stupenek, kotorye razlichny v sluchayakh parallel'noi i antiparallel'noi orientatsii magnitnykh momentov v kontaktakh. Vklady v tok ot uprugikh i neuprugikh protsessov rassmotreny otdel'no. Naideno, chto v neuprugoi chasti toka ko-tunnelirovaniya est' interferentsionnaya chast' (zavisimost' ot faz tunnel'nykh amplitud). |
Department of quantum mesoscopics: seminar, Friday, November 12, 2010, Landau ITP, 3:00 pm I.S. Burmistrov, Ya.V. Fominov Soobshcheniya o zadachakh, nakhodyashchikhsya v rabote |
Department of quantum mesoscopics: seminar, Friday, October 29, 2010, Landau ITP, 3:00 pm V. V. Pogosov (Institut teoreticheskoi i prikladnoi elektrodinamiki, Moskva) Uravneniya Richardsona i energiya svyazi kuperovskoi pary Izuchaetsya perekhod ot dvukhchastichnoi zadachi Kupera k mnogochastichnoi modeli Bardina-Kupera-Shriffera (BKSh). Dlya opisaniya osnovnogo sostoyaniya sistemy predlozhen analiticheskii sposob resheniya uravnenii Richardsona, matematicheski ogranichennyi razrezhennym predelom kuperovskikh par. Nesmotrya na eto ogranichenie, sopostavlenie s rezul'tatami teorii BKSh ukazyvaet na to, chto poluchennye rezul'taty ostayutsya tochnymi i v plotnom rezhime par. Predlagaetsya al'ternativnaya interpretatsiya rezul'tatov teorii BKSh dlya energii osnovnogo sostoyaniya v terminakh "energii svyazi kuperovskoi pary", evolyutsioniruyushchei prostym obrazom pri perekhode ot razrezhennogo k plotnomu rezhimu par. V etom podkhode shchel' tipa BKSh v spektre vozbuzhdenii yavlyaetsya pryamym sledstviem mnogochastichnykh effektov, vyzvannykh blokirovkoi otdel'nykh odnoelektronnykh sostoyanii. |
Department of quantum mesoscopics: seminar, Friday, October 22, 2010, Landau ITP, 3:00 pm M.V. Feigel'man, M.A. Skvortsov Soobshcheniya o zadachakh, nakhodyashchikhsya v rabote |
Department of quantum mesoscopics: seminar, Friday, October 1, 2010, Landau ITP, 3:00 pm Yulii Nazarov (Delft) Phase-slip oscillator and other Coulomb blockade devices |
Department of quantum mesoscopics: seminar, Tuesday, June 29, 2010, Kapitza Institute, 12:00 pm Joel Moore (Berkeley) Topological insulators, magnetoelectric coupling and Majorana fermions |
Department of quantum mesoscopics: seminar, Friday, April 9, 2010, Landau ITP, 3:00 pm I.S. Burmistrov Dephasing at the integer quantum Hall transitions: Short-ranged interaction in the singlet channel Temperaturnaya zavisimost' provodimosti na perekhode mezhdu plato v rezhime tselochislennogo kvantovogo effekta Kholla opredelyaetsya kriticheskim indeksom κ, kotoryi est' otnoshenie indeksa korrelyatsionnoi dliny (ν) i indeksa dliny razfazirovki (p), κ=p/(2ν). V otlichie ot indeksa korrelyatsionnoi dliny, kotoryi mnogo raz vychislyalsya, indeks p izuchalsya tol'ko v rabotakh [1,2]. V etikh rabotakh indeks p dliny razfazirovki byl vychislen v predpolozhenii, chto on opredelyaetsya anomal'noi razmernost'yu irrelevantnogo operatora, vkhodyashchego v `inverse participation ratio'. V rabote my analiticheski pokazyvaem, chto dlya sluchaya ekranirovannogo kulonovskogo vzaimodeistviya v singletnom kanale eto predpolozhenie vypolnyaetsya dlya Andersonovskogo perekhoda v unitarnom klasse v razmernosti 2+ε. Provedennye chislennye raschety ukazyvayut na to, chto eto predpolozhenie vypolnyaetsya i dlya perekhoda mezhdu plato. |
Department of quantum mesoscopics: seminar, Friday, March 19, 2010, Landau ITP, 3:00 pm Ya.I. Rodionov, I.S. Burmistrov, N.M. Shchelkachev Dinamika relaksatsii elektronov v zadache o kulonovskoi blokade My issleduem relaksatsionnuyu dinamiku elektronov v odnoelektronnom tranzistore. Imenno, my otvechaem na sleduyushchii vopros. Predpolozhim, chto neravnovesnoe elektronnoe raspredelenie obrazovalos' v protsesse eksperimenta. Po kakomu zakonu ono budet relaksirovat' k ravnovesiyu? Issledovanie relaksatsii provedeno v rezhimakh slaboi i sil'noi kulonovskoi blokady. Vyvedeny i resheny osnovnye kvantovye kineticheskie uravneniya, upravlyayushchie dinamikoi funktsii raspredeleniya v protsesse ustanovleniya teplovogo ravnovesiya. Ustanovleny universal'nye formuly dlya transportnykh koeffitsientov, prigodnye dlya tranzistora s tunnel'noi svyaz'yu lyuboi prozrachnosti. Krome togo, osushchestvlena odnopetlevaya perenormirovka osnovnykh fizicheskikh velichin, opredelyayushchikh transportnye nablyudaemye, chto pozvolyaet nam poluchit' naibolee tochnye rezul'taty. |
Department of quantum mesoscopics: seminar, Friday, March 12, 2010, Landau ITP, 3:00 pm Evgenii Mozgunov (student 5 kursa MFTI) Issledovanie osnovnogo sostoyaniya (T=0) dvumernoi Boze-zhidkosti metodom molekulyarnoi dinamiki Budet predstavleny predvaritel'nye rezul'taty chislennogo issledovaniya spektra i korrelyatsionnykh funktsii v spetsial'noi modeli 2-mernoi Boze-zhidkosti (s nerelyativistskoi supersimmetriei), dopuskayushchei modelirovanie kvantovykh svoistv pri pomoshchi klassicheskoi molekulyarnoi dinamiki. |
Department of quantum mesoscopics: seminar, Friday, February 26, 2010, Landau ITP, 3:00 pm A. N. Rubtsov, MGU Metod dual'nykh fermionov: diagrammnoe razlozhenie okolo srednepolevykh reshenii dlya sil'nokorrelirovannykh sistem Dlya sistem s sil'nymi korrelyatsiyami, pri otsutstvii yavnogo malogo parametra, prakticheski edinstvennym effektivnym metodom opisaniya yavlyayutsya interpolirushchie teorii, osnovannye na priblizheniyakh effektivnoi sredy. V chastnosti, dlya opisaniya sistem sil'nokorrelirovannykh elektronov rasprostranenie poluchil dinamicheskii metod srednego polya (DMFT), polnost'yu opisyvayushchii fiziku lokal'nykh (na uzle reshetki) elektronnykh fluktuatsii, no prenebregayushchii prostranstvennoi dispersiei korrelyatsii. Predlagaemyi metod, startuya s rezul'tata DMFT, pozvolyaet uchest' effekty prostranstvennoi dispersii posredstvom regulyarnogo diagrammnogo razlozheniya. Metod osnovan na tochnom perekhode k ansamblyu dual'nykh peremennykh, gaussovo priblizhenie dlya kotorogo vosproizvodit DMFT, a diagrammnoe razlozhenie po nelineinosti pozvolyaet utochnit' etot rezul'tat. Dlya poluzapolnennoi modeli Khabbarda na kvadratnoi reshetke uchet prosteishei diagrammnoi popravki v rezhime sil'nykh korrelyatsii (U=8..16 t) pozvolyaet izbavit'sya ot nefizichnogo tsentral'nogo pika plotnosti odnoelektronnykh sostoyanii, a summirovanie lestnichnogo ryada - poluchit' antiferromagnitnuyu psevdoshchel'. Dlya modeli s dopirovaniem, opisano anizotropnoe razrushenie poverkhnosti Fermi v rezhime psevdoshcheli i effekty perenormirovki zakona dispersii vblizi osobennostei van Khova. |
Department of quantum mesoscopics: seminar, Friday, February 12, 2010, Landau ITP, 3:00 pm I.A.Dmitriev (Karlsruhe Institute of Technology i FTI im. A.F. Ioffe) Neravnovesnye magnetoostsillyatsii transportnykh koeffitsientov dvumernogo elektronnogo gaza Doklad posvyashchen neravnovesnoi kinetike dvumernogo elektronnogo gaza na vysokikh urovnyakh Landau v usloviyakh mikrovolnovogo oblucheniya i/ili sil'nogo (v tom chisle neodnorodnogo) elektricheskogo polya. Budet predstavlena teoriya (osnovannaya na reshenii kvantovogo kineticheskogo uravneniya v prisutstvii plavnogo i korotkodeistvuyushchego potentsiala primesei, a takzhe elektron-elektronnogo i elektron-fononnogo vzaimodeistviya), pozvolyayushchaya v ramkakh edinogo podkhoda opisat' razlichnye tipy ravnovesnykh i neravnovesnykh magnetoostsillyatsii, nablyudaemykh v eksperimente. Pomimo Shubnikovskikh ostsillyatsii, syuda otnosyatsya ostsillyatsii magnetosoprotivleniya, indutsirovannye sil'nym postoyannym tokom, mikrovolnovym oblucheniem, i rezonansnym vzaimodeistviem s teplovymi fononami, a takzhe kvantovye ostsillyatsii koeffitsienta pogloshcheniya mikrovoln i szhimaemosti elektronnogo gaza. Takzhe budet predstavlena teoriya fotogal'vanicheskikh yavlenii v neodnorodnom elektronnom gaze. Budet pokazano, chto fotoeds v takikh neravnovesnykh sistemakh voznikaet vsledstvie narusheniya sootnosheniya Enshteina mezhdu provodimost'yu i koeffitsientom diffuzii. |
Department of quantum mesoscopics: seminar, Friday, January 29, 2010, Landau ITP, 3:00 pm K.E. Nagaev, T.V. Kostyuchenko (IRE im. V.A. Kotel'nikova RAN) Vliyanie elektron-elektronnogo vzaimodeistviya na magnetosoprotivlenie v dvumernykh ballisticheskikh mikrokontaktakh Vychislyaetsya popravka k provodimosti Sharvina dvumernogo ballisticheskogo mikrokontakta s bol'shim chislom kvantovykh kanalov. Ona voznikaet iz-za elektron-elektronnogo vzaimodeistviya, i mozhet byt' poluchena uzhe v kvaziklassicheskom predele. Popravka polozhitel'na, vozrastaet s temperaturoi i rezko umen'shaetsya s rostom magnitnogo polya. Poluchennye rezul'taty kachestvenno i kolichestvenno ob'yasnyayut anomal'noe polozhitel'noe magnetosoprotivlenie v malykh polyakh, nedavno nablyudavsheesya na eksperimente. |
Department of quantum mesoscopics: seminar, Thursday, January 28, 2010, Kapitza Institute, 1:45 pm M. Reznikov, A.Yu. Kuntsevich, N. Tenekh, V.M. Pudalov, T. Klapvaik Izmereniya termodinamicheskoi spinovoi namagnichennosti 2D sistemy We report thermodynamic magnetization measurements of a 2-dimensional electron gas for several high mobility Si-MOSFETs. The low-temperature magnetization is shown to be strongly sub-linear function of the magnetic field. The susceptibility determined from the zero-field slope grows with cooling as 1/Tα, with α=2.4±0.2 even at high electron densities, in apparent contradiction with the Fermi-liquid picture. |
Department of quantum mesoscopics: seminar, Thursday, January 14, 2010, Kapitza Institute, 11:30 am I.S. Burmistrov Topological Mott Insulators izlozhenie rezul'tatov preprintov: |
Department of quantum mesoscopics: seminar, Friday, December 18, 2009, Landau ITP, 3:00 pm Ya.I. Rodionov, I.S. Burmistrov, N.M. Shchelkachev Neravnovesnaya kulonovskaya blokada v odno-elektronnom tranzistore Izuchaetsya kulonovskaya blokada v odno-elektronnom tranzistore v neravnovesnom rezhime (naprimer, kogda temperatura ostrovka bol'she temperatury rezervuarov). V sluchae tunnel'nykh kontaktov mezhdu ostrovkom i rezervuarami polucheno kvantovoe kineticheskie uravnenie na funktsiyu raspredeleniya elektronov na ostrovke. S pomoshch'yu nego reshena zadacha o relaksatsii temperatury ostrovka za schet mekhanizma tunnelirovaniya elektronov s ostrovka v rezervuary i obratno. |
Department of quantum mesoscopics: seminar, Friday, December 11, 2009, Landau ITP, 4:00 pm I. S. Burmistrov Soobshchenie o zadachakh, nakhodyashchikhsya v rabote |
Department of quantum mesoscopics: seminar, Friday, December 11, 2009, Landau ITP, 3:00 pm I. A. Sadovskii, G. B. Lesovik i T. Martin Vliyanie fononov na zaryadovye sostoyaniya v andreevskoi kvantovoi tochke V rabote izuchaetsya zaryad v kvantovoi tochke, prisoedinennoi k sverkhprovodyashchim beregam pri nalichii kulonovskogo i elektron-fononnogo vzaimodeistvii v predele beskonechnoi sverkhprovodyashchei shcheli. Rassmotreno vliyanie fononov na chuvstvitel'nost' zaryada k raznitse sverkhprovodyashchikh faz. Pokazano, chto, v nekotorom smysle, elektron-fononnoe vzaimodeistvie deistvuet kak "otritsatel'noe" kulonovskoe vzaimodeistvie. |
Department of quantum mesoscopics: seminar, Friday, December 4, 2009, Landau ITP, 3:00 pm M. A. Skvortsov Soobshchenie o zadachakh, nakhodyashchikhsya v rabote |
Department of quantum mesoscopics: seminar, Friday, November 27, 2009, Landau ITP, 3:00 pm V. Kravtsov Critical random matrix ensembles, Luttinger liquid formalism and sonic analogues of black holes I will review old and recent results for eigenfunction and eigenvalue statisitics of certain random matrix ensembles and show the correspondence between them and statistics in the 3D Anderson model at criticality. From the conventional viewpoint of RMT the two ensembles belong to distinctly different universality classes, being invariant and non-invariant with respect to rotation of basis, respectively. Yet we show the similarity of their level statistics and a possibility of unifying them using the Luttinger liquid formalism. We also show that the level correlations in the invariant RMT show properties similar to expected density correlations in the sonic analogue of black holes. |
Department of quantum mesoscopics: seminar, Friday, November 13, 2009, Landau ITP, 3:00 pm D. Lyubshin Topologicheskie izolyatory s simmetriei otnositel'no obrashcheniya vremeni Planiruetsya rasskazat' o topologicheskikh izolyatorakh s T-simmetriei so "standartnoi" tochki zreniya (polyarizatsiya otnositel'no obrashcheniya vremeni pervichna, poverkhnostnye urovni vtorichny) po stat'yam Fu i Kane "Time reversal polarization and adiabatic spin pump" (2006) i "Topological insulators with inversion symmetry" (2007). Esli poluchitsya, to mozhno budet zadet' i obshchuyu klassifikatsiyu po Kitaevu. |
Department of quantum mesoscopics: seminar, Friday, October 16, 2009, Landau ITP, 3:00 pm K.S.Tikhonov Referativnyi doklad po rabote arXiv:0810.0340 Exactly solvable pairing model for superconductors with a p+ip-wave symmetry Authors: Miguel Ibanez, Jon Links, German Sierra, Shao-You Zhao |
Department of quantum mesoscopics: seminar, Friday, October 9, 2009, Landau ITP, 3:00 pm M.Feigel'man Kvantovyi fazovyi perekhod "sverkhprovodnik-izolyator" v spinovoi modeli na reshetke Bete (sovmestno s L.Ioffe i M.Mezard) |
Department of quantum mesoscopics: seminar, Friday, October 2, 2009, Landau ITP, 3:00 pm I. Burmistrov soobshchenie o rabote Magnetic Impurities on the Surface of a Topological Insulator, Qin Liu, Chao-Xing Liu, Cenke Xu, Xiao-Liang Qi, Shou-Cheng Zhang Phys Rev Lett 102, 156603 (2009) v kotoroi izuchaetsya RKKY vzaimodeistvie na poverkhnosti topologicheskogo izolyatora, a takzhe o ryade rabot svyazannykh s etim voprosom. |
Department of quantum mesoscopics: seminar, Friday, September 25, 2009, Bol'shaya gostinaya Doma Uchenykh, 11:30 am rasshirennoe zasedanie Uchenogo soveta ITF, posvyashchennoe yubileyu Sergeya Viktorovicha Iordanskogo V programme zasedaniya: |
Department of quantum mesoscopics: seminar, Friday, September 18, 2009, Landau ITP, 3:00 pm I. Burmistrov Spinovye i zaryadovye korrelyatsii v kvantovykh tochkakh: tochnoe reshenie (dlya tunnel'noi plotnosti sostoyanii) Spin and Charge Correlations in Quantum Dots: An Exact Solution (for the Tunneling Density of States) I.Burmistrov, Y. Gefen, M. Kiselev Abstract: The inclusion of charging and spin-exchange interactions within the Universal Hamiltonian description of quantum dots is challenging as it leads to a non-Abelian action. Here we present an exact analytical solution of the probem, in particular, in the vicinity of the Stoner instabilty point. We specifically calculate the tunneling density of states (TDOS) and the spin susceptibility. Near the instability point the TDOS exhibits a non-monotonous behavior as function of the tunneling energy, even at temperatures higher than the exchange energy. Our approach is generalizable to a broad set of observables, including the a.c. susceptibility and the absorption spectrum for anisotrpic spin interaction. Our results could be tested in nearly ferromagnetic materials. |
Department of quantum mesoscopics: seminar, Thursday, September 17, 2009, Kapitza Institute, 11:30 am M.V. Feigel'man Topologicheskie izolyatory (obzor literatury - prodolzhenie) |
Department of quantum mesoscopics: seminar, Friday, September 11, 2009, Landau ITP, 3:00 pm M.V.Feigel'man Topologicheskie izolyatory (obzor literatury) |
Department of quantum mesoscopics: seminar, Friday, September 4, 2009, Landau ITP, 3:00 pm Ya.V.Fominov doklad po eksp. stat'e arxiv:0906.3644 Discovery of parity-violating Majorana fermions in a chiral superconductor SrRu2O4 |
Department of quantum mesoscopics: seminar, Tuesday, June 30, 2009, RAS Presidium, 712, 3:00 pm P.M.Ostrovskii O topologicheskikh izolyatorakh-3 |
Department of quantum mesoscopics: seminar, Friday, June 19, 2009, Landau ITP, 3:00 pm P.M.Ostrovskii O topologicheskikh izolyatorakh-2 |
Department of quantum mesoscopics: seminar, Thursday, June 18, 2009, RAS Presidium, 712, 3:00 pm P.M.Ostrovskii O topologicheskikh izolyatorakh |
Department of quantum mesoscopics: seminar, Friday, May 29, 2009, Landau ITP, 3:00 pm S. I. Dorozhkin (IFTT) Znakoperemennye magnetoostsillyatsii fototoka i foto-EDS v dvumernykh elektronnykh sistemakh pod SVCh oblucheniem Eksperimental'no obnaruzheny znakoperemennye ostsillyatsii fototoka i foto-EDS, voznikayushchie pri mikrovolnovom obluchenii neodnorodnykh obraztsov s dvumernymi elektronnymi sistemami. Polozhenie ostsillyatsii sootvetstvuet polozheniyu garmonik tsiklotronnogo rezonansa. Pokazano, chto vozniknovenie fotosignalov svyazano so vstroennym v obraztse elektricheskim polem. V etom sluchae ostsillyatsii fototoka sootvetstvuyut ego protekaniyu vdol' i protiv elektricheskogo polya, a ostsillyatsii foto-EDS otrazhayut libo ekranirovanie, libo usilenie elektricheskogo polya foto-vozbuzhdennymi elektronami. V teoreticheskoi chasti raboty pokazano, chto vozniknovenie foto-gal'vanicheskikh signalov svyazano s narusheniem v neravnovesnom sostoyanii sootnosheniya Einshteina mezhdu provodimost'yu i koeffitsientom diffuzii. Vychislennye provodimost' i koeffitsient diffuzii dvumernoi elektronnoi sistemy pod oblucheniem, a takzhe vol't-ampernaya kharakteristika obraztsa s omicheskimi kontaktami pozvolyayut ob'yasnit' eksperimental'nye nablyudeniya. [1] S.I. Dorozhkin, I.V. Pechenezhskii, L.N. Pfeiffer, K.W. West, V. Umansky, K. von Klitzing, J.H. Smet, Photocurrent and photovoltage oscillations in the two-dimensional electron system: enhancement and suppression of built-in electric fields, Phys. Rev. Lett. 102, 036602 (2009). [2] I.A. Dmitriev, S.I. Dorozhkin, and A.D. Mirlin, Theory of the microwave-induced photocurrent and photovoltage magneto-oscillations in a spatially non-uniform 2D electron gas. |
Department of quantum mesoscopics: seminar, Friday, April 17, 2009, Landau ITP, 3:00 pm G.B.Lesovik 1) Kvantovomekhanicheskii vyvod zakona vozrastaniya entropii dlya prostoi modeli simmetrichnogo kvantovogo bluzhdaniya 2) Quantum divisibility test and its application in mesoscopic physics [G.B.Lesovik, M.V.Suslov, and G.Blatter] Quantum mechanics offers novel algorithms speeding up the solution of specific computational tasks. While applications in quantum cryptography are close to commercial realization, building a universal quantum computer with thousands of quantum bits lies in the distant future, if ever realized. In this situation, it is interesting to consider special tasks, less demanding in their requirements regarding the number of qubits and the network complexity. Here, we discuss an algorithm and its application where a few qubits serve as active or passive detectors. The core algorithmic element is a setup with K qubits allowing to count the elements in a stream of particles flowing in a quantum wire and represent it in a binary form. Applications include a divisibility-check to experimentally determine the size of a finite train of particles in a quantum wire and a scheme allowing to entangle multi-particle wave functions in a Mach-Zehnder interferometer, generating Bell-, Greenberger-Horne-Zeilinger-, or Dicke states. |
Department of quantum mesoscopics: seminar, Friday, April 10, 2009, Landau ITP, 3:00 pm O. Cepas (Lab. J.-V. Poncelet, Moscow, and Institut Ne'el, Grenoble) Quantum spin liquids and ordered phases in the Kagome Antiferromagnet |
Department of quantum mesoscopics: seminar, Friday, March 20, 2009, Landau ITP, 3:00 pm I.V.Kukushkin, M.V.Lebedev Gigantskie opticheskie fluktuatsii v rezhime kvantovogo effekta Kholla |
Department of quantum mesoscopics: seminar, Friday, March 13, 2009, Landau ITP, 3:00 pm M.V.Feigel'man |
Department of quantum mesoscopics: seminar, Friday, March 6, 2009, Landau ITP, 3:00 pm A.S.Ioselevich Mott insulating state in ultraclean carbon nanotubes referativnyi doklad po eksperimental'noi rabote V.Deshpandei, D.Novikov, M.Bockgrath et al, Science, v.323, p.106 (2009) |
Department of quantum mesoscopics: seminar, Friday, February 27, 2009, Landau ITP, 3:00 pm K.S. Tikhonov Phenomenology of one-dimensional quantum liquids beyond low energy limit referativnyi doklad po rabote L. Glazman, A. Imambekov, arXiv:0812.1046 |
Department of quantum mesoscopics: seminar, Friday, January 30, 2009, Landau ITP, 3:00 pm Rodionov Ya.I., Burmistrov I.S., Ioselevich A.S. Soprotivlenie zaryadovoi relaksatsii v zadache o kulonovskoi blokade Issleduetsya zadacha o dissipatsii energii v zadache o metallicheskom ostrovke, soedinennym tunnel'nym kontaktom s rezervuarom, i emkost'yu s zatvorom, na kotoroe podaetsya peremennoe napryazhenie. Formuly dlya dissipatsii energii s uchetom kulonovskoi energii na ostrovke polucheny v dvukh predel'nykh sluchayakh: malykh i bol'shikh kondaktansov tunnel'nogo kontakta. Poluchennye rezul'taty pozvolyayut sdelat' predpolozhenie ob universal'nosti poluchennykh formul pri lyubykh kondaktansakh tunnel'nogo perekhoda. |
Department of quantum mesoscopics: seminar, Friday, January 23, 2009, Landau ITP, 3:00 pm M.N. Serbin referativnyi doklad po rabote Lieb-Schultz-Mattis Theorem for quasi-topological systems, cond-mat/0508508 |
Department of quantum mesoscopics: seminar, Friday, December 19, 2008, Landau ITP, 4:00 pm N.M. Shchelkachev Soobshchenie o zadachakh, nakhodyashchikhsya v rabote |
Department of quantum mesoscopics: seminar, Friday, December 19, 2008, Landau ITP, 3:00 pm I.S. Burmistrov Soobshchenie o zadachakh, nakhodyashchikhsya v rabote |
Department of quantum mesoscopics: seminar, Friday, December 12, 2008, Landau ITP, 3:00 pm Ivan Protopopov Referativnyi doklad po rabote: arXiV:0802.0379 Creation and manipulation of anyons in the Kitaev model S. Dusuel, K. P. Schmidt, J. Vidal We analyze the effect of local spin operators in the Kitaev model on the honeycomb lattice. We show, in perturbation around the isolated-dimer limit, that they create Abelian anyons together with fermionic excitations which are likely to play a role in experiments. We derive the explicit form of the operators creating and moving Abelian anyons without creating fermions and show that it involves multi-spin operations. Finally, the important experimental constraints stemming from our results are discussed. |
Department of quantum mesoscopics: seminar, Friday, December 5, 2008, Landau ITP, 3:00 pm Yaroslav Rodionov Referativnyi doklad po eksperimental'noi rabote: Violation of Kirchhoff's Laws for a Coherent RC Circuit, J.Gabelli, et al, Science 313, 499 (2006) i obzor lezhashchei v ee osnove teoreticheskoi raboty: Buttiker, Thomas, Pretre, Phys. Lett. A 180, 364 (1993) |
Department of quantum mesoscopics: seminar, Friday, November 21, 2008, Landau ITP, 3:00 pm Konstantin Tikhonov Nestatsionarnyi effekt Dzhozefsona v SINIS perekhode (doklad o zadache, nakhodyashcheisya v rabote) Budet rasskazano o poluchennykh k nastoyashchemu vremeni analiticheskikh rezul'tatakh dlya SINIS perekhoda v rezhime zadannogo napryazheniya: vychislenie zavisyashchego ot vremeni toka v dissipativnom rezhime. |
Department of quantum mesoscopics: seminar, Friday, September 26, 2008, Landau ITP, 3:30 pm V.V.Ryazanov O vozmozhnostyakh modelirovaniya izingovskikh reshetok matritsami so sverkhprovodyashchimi pi-kontaktami |
Department of quantum mesoscopics: seminar, Friday, September 19, 2008, Landau ITP, 3:00 pm I.S.Burmistrov Referativnyi doklad po eksperimentam 1) M. Dolev, M. Heiblum, V. Umansky, A. Stern, D. Mahalu, "Observation of a quarter of an electron charge at the \nu=5/2 quantum Hall state", Nature 452, 829 (2008) [arXiV:0802.0930] 2) 2) I.P. Radu, J.B. Miller, C.M. Marcus, M.A. Kastner, L.N. Pfeiffer, K.W. West, "Quasi-particle properties from tunneling in the \nu=5/2 fractional quantum Hall state", Science 320, 899 (2008) [arXiV:0803.3530] |
Department of quantum mesoscopics: seminar, Friday, September 12, 2008, Landau ITP, 3:00 pm M.V.Feigel'man Soobshchenie o zadachakh, nakhodyashchikhsya v rabote |
Department of quantum mesoscopics: seminar, Friday, May 23, 2008, Landau ITP, 4:00 pm V.S. Khrapai (IFTT), A.A. Shashkin, M.G. Trokina, V.T. Dolgopolov i dr. Zavisimost' energeticheskikh shchelei v drobnom kvantovom effekte Kholla ot faktora zapolneniya (arXiv:0803.2737) |
Department of quantum mesoscopics: seminar, Friday, May 23, 2008, Landau ITP, 2:45 pm M. Feigel'man O vozmozhnosti mnogochastichnoi lokalizatsii na dielektricheskoi storone perekhoda sverkhprovodnik-izolyator (chast' II) |
Department of quantum mesoscopics: seminar, Friday, April 11, 2008, Landau ITP, 3:00 pm M. Feigel'man i I. Protopopov Rasskaz o konferentsii "Quantum Transport and Nanophysics" (Moriond, mart 2008) |
Department of quantum mesoscopics: seminar, Friday, April 4, 2008, Landau ITP, 3:00 pm Ya. Fominov i N. Shchelkachev Rasskaz o konferentsii "Nanofizika i nanoelektronika" (Nizhnii Novgorod, mart 2008) |
Department of quantum mesoscopics: seminar, Friday, April 4, 2008, Landau ITP, 3:00 pm Ya. Fominov Referativnyi doklad po rabotam Bergeret, Volkov, Efetov, "Induced ferromagnetism due to superconductivity in superconductor- ferromagnet structures", PRB 69, 174504 (2004); "Spin screening of magnetic moments in superconductors", Europhys. Lett. 66, 111 (2004). |
Department of quantum mesoscopics: seminar, Friday, March 28, 2008, Landau ITP, 3:00 pm S.V.Iordanskii Vikhrevye reshetki i kvantovyi effekt Kholla |
Department of quantum mesoscopics: seminar, Friday, January 25, 2008, Landau ITP, 3:00 pm A.V. Lebedev Asimmetriya kodaktansa vzaimodeistvuyushchei kvantovoi tochki Rassmotren kondaktans kvantovoi tochki s kulonovskim vzaimodeistviem v situatsii, kogda na tochku posylaetsya konechnoe chislo odnoelektronnykh volnovykh paketov. Iskhodya iz znaniya tochnoi N chastichnoi matritsy rasseyaniya sistemy pokazano, chto v sluchae nesimmetrichnoi kvantovoi tochki (otnositel'no zameny levo/pravo) pri nalichii vzaimodeistviya kondaktans sistemy okazyvaetsya takzhe asimmetrichnym otnositel'no napravleniya perenosa zaryada. |
Department of quantum mesoscopics: seminar, Friday, January 11, 2008, Landau ITP, 3:00 pm I.S. Burmistrov, N.M. Shchelkachev Vliyanie spinovogo i dolinnogo rasshchepleniya na transport v dvumernoi neuporyadochennoi elektronnoi zhidkosti V rabote issleduetsya vliyanie spinovogo i dolinnogo rasshcheplenii na soprotivlenie, spinovuyu i dolinnuyu vospriimchivost' dvumernoi neuporyadochennoi elektronnoi zhidkosti. Kak vyyasnilos', v rabote na etu zhe temu, rasskazannoi god nazad, nami byla dopushchena oshibka. V doklade budet rasskazano o novykh odnopetlevykh uravneniyakh renorm-gruppy, kotorye opisyvayut sistemu v dvukh oblastyakh Δs << T << Δv i T << Δs << Δv, gde T - temperatura, Δs -spinovoe rasshcheplenie, i Δv - dolinnoe rasshcheplenie. S pomoshch'yu poluchennykh uravnenii renorm-gruppy nam udalos' kachestvenno ob'yasnit' proiskhozhdenie nemonotonnoi zavisimosti soprotivleniya ot temperatury, kotoraya nablyudaetsya eksperimental'no v parallel'nom magnitnom pole, a takzhe predskazat' vozmozhnost' nablyudeniya novogo tipa nemonotonnogo povedeniya, pri kotorom soprotivlenie kak funktsiya temperatury imeet dva maksimuma. |
Department of quantum mesoscopics: seminar, Friday, December 7, 2007, Landau ITP, 3:00 pm Konstantin Bayandin Sboi fazy pri neravnovesnom sverkhprovodyashchem toke cherez kvantovuyu tochku V priblizhenii tunnel'nogo gamil'toniana rassmatrivaetsya model' kvantovoi tochki, pomeshchennoi mezhdu dvumya sverkhprovodyashchimi provodnikami, k kotorym prilozhena raznost' potentsialov. Dopolnitel'no ryadom s tochkoi pomeshchen normal'nyi provodnik, po kotoromu ne techet tok: on igraet rol' rezervuara, sbivayushchego fazu tunneliruyushchikh v nego elektronov. Pri pomoshchi neravnovesnoi Keldyshevskoi tekhniki vychislyaetsya podshchelevoi elektricheskii tok, kotoryi, kak izvestno, voznikaet v protsesse perenosa zaryada pri mnozhestvennykh Andreevskikh otrazheniyakh. Pokazano, chto svyaz' s normal'nym provodnikom privodit k sglazhivaniyu osobennostei v postoyannom toke, voznikayushchikh pri mnozhestvennykh Andreevskikh otrazheniyakh. S drugoi storony, pervaya garmonika toka na Dzhozefsonovskoi chastote bolee ustoichiva k sboyu fazy, dazhe dlya napryazhenii, men'shikh sverkhprovodyashchei shcheli. Faza etoi pervoi garmoniki pozvolyaet provodit' izuchenie effektov, vyzvannykh normal'nym provodnikom. |
Department of quantum mesoscopics: seminar, Friday, October 26, 2007, Landau ITP, 3:00 pm M.N.Serbin Referativnyi doklad po rabote R. W. Cherng, L. S. Levitov, Entropy and correlation functions of a driven quantum spin chain, Phys. Rev. A 73, 043614 (2006) |
Department of quantum mesoscopics: seminar, Friday, October 5, 2007, Landau ITP, 3:00 pm V.R. Kogan Interferentsionnye popravki k korrelyatsionnoi funktsii urovnei v billiarde Sinaya Na primere billiarda Sinaya izucheno vliyanie difraktsii na spektral'nye kharakteristiki khaoticheskikh billiardov, granitsa kotorykh imeet vognutye vovnutr' uchastki. Difraktsiya privodit k poyavleniyu tselogo mnozhestva dopolnitel'nykh traektorii pomimo klassicheskikh. Vychislen "nediagonal'nyi" vklad ot nikh v korrelyatsionnuyu funktsiyu dvukh urovnei energii, proiskhodyashchii ot interferentsii mezhdu nimi. Pokazano, chto on yavlyaetsya ostsilirruyushchei funktsiei chastoty s periodom, ravnym t.n. vremeni Erenfesta. |
Department of quantum mesoscopics: seminar, Friday, September 28, 2007, Landau ITP, 3:00 pm K. Tikhonov Dzhozefsonovskii tok cherez grafen (obzor eksp. i teorii) |
Department of quantum mesoscopics: seminar, Friday, June 15, 2007, Landau ITP, 3:00 pm Ya. Rodionov Nelokal'nyi kharakter soprotivleniya v granulirovannoi sisteme Issleduyutsya instantonnye popravki k soprotivleniyu v neodnorodnom granulirovannom metalle. Obsuzhdaetsya kachestvennaya fizicheskaya kartina fiziki sistemy v sluchae prosteishei neodnorodnosti. |
Department of quantum mesoscopics: seminar, Friday, May 18, 2007, Landau ITP, 3:00 pm S.V. Iordanskii |
Department of quantum mesoscopics: seminar, Friday, May 11, 2007, Landau ITP, 3:00 pm I.A. Sadovskii, G.B. Lesovik, Dzh. Blatter O vozmozhnosti registratsii slabykh magnitnykh potokov s pomoshch'yu andreevskoi kvantovoi tochki Zaryad podshchelevogo sostoyaniya v andreevskoi kvantovoi tochke (AKT), pomeshchennoi v sverkhprovodyashchuyu petlyu, ochen' chuvstvitelen k magnitnomu potoku, pronikayushchemu v petlyu. My obsuzhdaem vozmozhnost' ispol'zovaniya etoi ustanovki kak pribora dlya izmereniya slabykh magnitnykh potokov. My detal'no izuchili chuvstvitel'nost' kak funktsiyu parametrov AKT v predele Δ → ∞. Takzhe my izuchili slaboe kulonovskoe vzaimodeistvie v AKT. |
Department of quantum mesoscopics: seminar, Friday, April 6, 2007, Landau ITP, 3:00 pm I. Protopopov, M. Feigel'man Dual'nost' sverkhprovodnik-izolyator v setke iz dzhozefsonovskikh provolochek My predlagaem novuyu model'nuyu sistemu dlya izucheniya perekhoda sverkhprovodnik-izolyator. Eta sitema predstavlyaet soboi regulyarnuyu reshetku, kazhdoe rebro kotoroi sostoit iz N>>1 dzhozefsonovskikh kontaktov, soedinennykh posledovatel'no. Dlya sluchaya, kogda dzhozefsonovskaya energiya kontaktov velika po sravneniyu s zaryadovoi, razvita teoriya, opisyvayushchaya takuyu setku. Vyvedeno tochnoe dual'noe preobrazovanie, perevodyashchee gamil'tonian iskhodnoi sistemy v standartnyi gamil'tonian dzhozefsonovskoi setki na kvadratnoi reshetke. Dlya magnitnykh frustratsii f=0, 1/2, 1/4 naideno kriticheskoe otnoshenie E_J/E_C, pri kotorom v rassmatrivaemoi sisteme proiskhodit nul'temperaturnyi perekhod sverkhprovodnik-izolyator, i opredelena zavisimot' temperatury sverkhprovodyashchego perekhoda ot E_J/E_C. Analogichnye velichiny otseneny dlya sluchaya nulevoi magnitnoi frustratsii, no v prisutstvii sil'noi sluchainoi zaryadovoi frustratsii. |
Department of quantum mesoscopics: seminar, Friday, March 23, 2007, Landau ITP, 3:00 pm K.V. Bayandin, A.V. Lebedev, G.B. Lesovik Ob izmerenii korrelyatorov toka vysshikh poryadkov V rabote rassmatrivaetsya vopros ob izmerimosti fluktuatsii toka vysshikh poryadkov lineinym detektorom. Rassmotreny dva razlichnykh tipa izmerenii: izmerenie spektral'noi moshchnosti fluktuatsii i izmerenie raznovremennykh korrelyatorov toka pri fiksirovannykh vremenakh. Dlya kazhdogo sluchaya polucheny formal'no tochnye vyrazheniya dlya pokazanii detektora, soderzhashchie uporyadochennye vdol' Keldyshevskogo kontura operatory elektronnogo toka. Naiden yavnyi vid vremennogo uporyadocheniya operatorov toka pod znakom srednego pri izmerenii raznovremennykh korrelyatorov toka vysshikh poryadkov. Rassmotrena situatsiya, kogda detektor izmeryaet korrelyatsii toka v razlichnykh tochkakh provodnika. |
Department of quantum mesoscopics: seminar, Friday, March 16, 2007, Landau ITP, 3:00 pm K. Tikhonov soobshchenie po rabote A.V. Shytov "Structured Energy Distribution and Coherent AC Transport in Mesoscopic Wires", Phys. Rev. B 71, 085301 (2005) |
Department of quantum mesoscopics: seminar, Friday, September 8, 2006, Landau ITP, 3:00 pm Evgenii Lakshtanov (Mat.fakul'tet universiteta g.Aveiro, Portugaliya) Transportnoe sechenie rasseyaniya: podschet i voprosy optimizatsii My rassmotrim zadachu o rasseyanii ploskoi volny na prepyatstvii ili neodnorodnostyakh. Transportnoe sechenie rasseyaniya sigma_T malo izucheno dazhe dlya potentsialov obladayushchikh tsentral'noi simmetriei. V sluchae zhe prepyatstviya proizvol'noi formy amplituda rasseyaniya prakticheski ne poddaetsya informativnomu analiticheskomu opisaniyu. Tem ne menee, v nekotorykh sluchayakh nam udalos' poluchit' nekotoruyu informatsiyu, vychislyaya i sravnivaya polnoe i transportnoe secheniya rasseyaniya, a takzhe reshaya zadachu o minimizatsii (maksimizatsii) sigma_T. |
Department of quantum mesoscopics: seminar, Friday, January 27, 2006, Landau ITP, 3:00 pm Revaz Ramazashvili (Max Planck Institute, Dresden) Geizenbergovskii obmen v kvantovoi provoloke v rezhime nizkoi plotnosti Pri nizkoi plotnosti, elektrony v kvantovoi provoloke mogut obrazovat' vignerovskii kristall. V etom sluchae geizenbergovskii obmen mezhdu paroi blizhaishikh elektronov voznikaet v rezul'tate tunnelirovaniya pod razdelyayushchim ikh kulonovskim bar'erom. Pri etom kulonovskoe vzaimodeistvie vovlekaet v protsess tunnelirovaniya i vse ostal'nye elektrony, ch'e vliyanie na velichinu konstanty geizenbergovskogo obmena my i izuchaem - kak analiticheski, tak i chislenno. |
Department of quantum mesoscopics: seminar, Friday, November 18, 2005, Landau ITP, 3:00 pm K. Bayandin, G.B. Lesovik Zaputannye po energii sostoyaniya v NS sisteme |
Department of quantum mesoscopics: seminar, Friday, October 7, 2005, Landau ITP, 3:00 pm I.S.Burmistrov Theta renormalization and the Coulomb blockade problem |
Department of quantum mesoscopics: seminar, Friday, September 30, 2005, Landau ITP, 3:00 pm Ol'ga Dimitrova Sverkhprovodyashchii kontakt cherez dvumernyi elektronnyi gaz so spin-orbital'nym vzaimodeistviem Rashby |
Department of quantum mesoscopics: seminar, Friday, September 23, 2005, Landau ITP, 3:00 pm A.Lebedev doklad po materialam dissertatsii |
Department of quantum mesoscopics: seminar, Thursday, May 26, 2005, RAS Presidium, 712, 2:30 pm M.A.Skvortsov, D.A.Ivanov |
Department of quantum mesoscopics: seminar, Thursday, April 28, 2005, RAS Presidium, 712, 2:30 pm Andrei Lebedev (ITF), G.B. Lesovik i G. Blatter Pulsed spin-entangled electron pairs on demand |
Department of quantum mesoscopics: seminar, Friday, April 1, 2005, Landau ITP, 3:00 pm Yakov Fominov, ITF Kriticheskoe sostoyanie mezoskopicheskogo sverkhprovodnika po rabote R.S. Keizer, M.G. Flokstra, J. Aarts i T. M. Klapwijk |
Department of quantum mesoscopics: seminar, Friday, March 25, 2005, Landau ITP, 3:00 pm Andrei Lebedev, ITF Zatseplenie v nevzaimodeistvuyushchei mezoskopicheskoi sisteme |
Department of quantum mesoscopics: seminar, Friday, March 18, 2005, Landau ITP, 3:00 pm Andrei Lebedev, ITF |
Department of quantum mesoscopics: seminar, Friday, October 15, 2004, Landau ITP, 3:00 pm Nikolai Shchelkachev, ITF Perekhody mezhdu pi i 0 sostoyaniyami v SFS kontaktakh |
Department of quantum mesoscopics: seminar, Friday, September 3, 2004, Landau ITP, 3:00 pm Irina Bobkova, IFTT Analog andreevskogo otrazheniya na granitse s antiferromagnetikom |
Department of quantum mesoscopics: seminar, Friday, February 20, 2004, Landau ITP, 3:00 pm M. Kharitonov Nemonotonnaya zavisimost' Tc(H) v sverkhprovodyashchei plenke so spin-orbital'nymi magnitnymi primesyami |