27 March 2025 Thu 4 pm

Models with correlated disorders are rather common in physics. In some of them, like the Aubry-André (AA) model, the localization phase diagram can be found from the (self)duality with respect to the Fourier transform. In the others, like the all-to-all translation-invariant Rosenzweig-Porter (TI RP) ensemble or the Hilbert-space structure of the many-body localization, one needs to develop more sophisticated and usually phenomenological methods to find the localization transition. In addition, such models contain not only localization but also the ergodicity-breaking transition, giving way to the non-ergodic extended phase of states with non-trivial fractal dimensions D_q. 

In this talk, after a brief introduction to the topic of correlated long-range systems, I will consider a method [1] to calculate both the localization phase diagram and a lower bound to the fractal dimensions D_2 and D_\infty, relevant for physical observables, in the system with correlated on-site disorder. In order to verify this method, I will show the application of it to the class of long-range (self-)dual models, interpolating between AA and TI RP ones via both power-law dependences of on-site disorder correlations and hopping terms, and, thus, being out of the validity range of the previously developed methods. We show that the interplay of the correlated disorder and the power-law decaying hopping terms leads to the emergence of the two types of fractal phases in an entire range of parameters, even without having any quasiperiodicity of the AA potential. The analytical results of the above method are in full agreement with the extensive numerical calculations.

[1] Shilpi Roy, Saurabh Basu, Ivan M. Khaymovich, Ergodicity-breaking phase diagram and fractal dimensions in long-range models with generically correlated disorder, Phys. Rev. B 111, 104203 (2025) [arXiv:2307.03085].

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