Семинар сектора квантовой мезоскопики, пятница 29 мая 2020 г., webinar, 15:00|
Fragile ergodic phases in logarithmically-normal Rosenzweig-Porter model
Webinar link: http://bbb2.itp.ac.ru/b/qme-erf-krk
Gaussian Rosenzweig-Porter (GRP) random matrix ensemble is the only
one in which the robust multifractal phase have a status of a mathematical
theorem. In this paper we suggest an extension of the GRP model, the LN-RP model, by adopting a logarithmically-normal (LN) distribution of off-diagonal matrix elements. We show that large matrix elements from the tail of this distribution give rise to a peculiar weakly-ergodic phase that replaces both the multifractal and the fully-ergodic phases present in GRP ensemble. A new phase is characterized by the broken basis-rotation symmetry which the fully-ergodic phase respects. Thus in addition to the localization and ergodic
transitions in LN-RP model there exists also the FWT transition between the
two ergodic phases. We formulate the criteria of the localization, ergodic and FWT transitions and obtain the phase diagram of the model. We also suggest a new criteria of stability of the non-ergodic phases and prove that the Anderson transition in LN-RP model is discontinuous, in contrast to its GRP counterpart.