20.500.12556/RUL-165400 Fading ergodicity Eigenstate thermalization hypothesis (ETH) represents a breakthrough in many-body physics since it allows us to link thermalization of physical observables with the applicability of random matrix theory (RMT). Recent years were also extremely fruitful in exploring possible counterexamples to thermalization, ranging, among others, from integrability, single-particle chaos, many-body localization, many-body scars, to Hilbert-space fragmentation. In all these cases the conventional ETH is violated. However, it remains elusive how the conventional ETH breaks down when one approaches the boundaries of ergodicity, and whether the range of validity of the conventional ETH coincides with the validity of RMT-like spectral statistics. Here we bridge this gap and we introduce a scenario of the ETH breakdown in many-body quantum systems, dubbed fading ergodicity regime, which establishes a link between the conventional ETH and nonergodic behavior. We conjecture this scenario to be relevant for the description of finite many-body systems at the boundaries of ergodicity, and we provide numerical and analytical arguments for its validity in the quantum sun model of ergodicity-breaking phase transition. For the latter, we provide evidence that the breakdown of the conventional ETH is not associated with the breakdown of the RMT-like spectral statistics. ergodicity eigenstate thermalization many-body localization random matrix theory ergodičnost termalizacija lastnih stanj lokalizacija teorija naključnih matrik true false true Angleški jezik Slovenski jezik Članek v reviji 2024-12-05 11:33:32 2024-12-05 11:33:32 2024-12-06 03:51:41 0000-00-00 00:00:00 2024 0 0 Str. 134206-1-134206-12 iss. 13 Vol. 110 2024 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 536.9 2469-9950 10.1103/PhysRevB.110.134206 217704195 PhysRevB.110.134206.pdf PhysRevB.110.134206.pdf 1 9A1D5C9B449414E145CC0EB58C732842 c82610f34a13ad95781bceee2f512bfd3b51e9d13ddb8d503d819eb2572f887f 104d8c77-b2f4-11ef-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=196533 https://journals.aps.org/prb/abstract/10.1103/PhysRevB.110.134206 0 179768c1-b2f4-11ef-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=196534 Fakulteta za matematiko in fiziko 0 0 0