{"alternative_title":["ISTA Thesis"],"status":"public","related_material":{"record":[{"id":"11470","relation":"part_of_dissertation","status":"public"},{"id":"8308","relation":"part_of_dissertation","status":"public"},{"status":"public","relation":"part_of_dissertation","id":"11469"},{"id":"12750","relation":"part_of_dissertation","status":"public"}]},"title":"Ergodicity breaking in disordered and kinetically constrained quantum many-body systems","publisher":"Institute of Science and Technology Austria","date_created":"2023-03-17T13:30:48Z","user_id":"8b945eb4-e2f2-11eb-945a-df72226e66a9","oa_version":"None","oa":1,"abstract":[{"text":"Nonergodic systems, whose out-of-equilibrium dynamics fail to thermalize, provide a fascinating research direction both for fundamental reasons and for application in state of the art quantum devices.\r\nGoing beyond the description of statistical mechanics, ergodicity breaking yields a new paradigm in quantum many-body physics, introducing novel phases of matter with no counterpart at equilibrium.\r\nIn this Thesis, we address different open questions in the field, focusing on disorder-induced many-body localization (MBL) and on weak ergodicity breaking in kinetically constrained models.\r\nIn particular, we contribute to the debate about transport in kinetically constrained models, studying the effect of $U(1)$ conservation and inversion-symmetry breaking in a family of quantum East models.\r\nUsing tensor network techniques, we analyze the dynamics of large MBL systems beyond the limit of exact numerical methods.\r\nIn this setting, we approach the debated topic of the coexistence of localized and thermal eigenstates separated by energy thresholds known as many-body mobility edges.\r\nInspired by recent experiments, our work further investigates the localization of a small bath induced by the coupling to a large localized chain, the so-called MBL proximity effect.\r\n\r\nIn the first Chapter, we introduce a family of particle-conserving kinetically constrained models, inspired by the quantum East model.\r\nThe system we study features strong inversion-symmetry breaking, due to the nature of the correlated hopping.\r\nWe show that these models host so-called quantum Hilbert space fragmentation, consisting of disconnected subsectors in an entangled basis, and further provide an analytical description of this phenomenon.\r\nWe further probe its effect on dynamics of simple product states, showing revivals in fidelity and local observalbes.\r\nThe study of dynamics within the largest subsector reveals an anomalous transient superdiffusive behavior crossing over to slow logarithmic dynamics at later times.\r\nThis work suggests that particle conserving constrained models with inversion-symmetry breaking realize new universality classes of dynamics and invite their further theoretical and experimental studies.\r\n\r\nNext, we use kinetic constraints and disorder to design a model with many-body mobility edges in particle density.\r\nThis feature allows to study the dynamics of localized and thermal states in large systems beyond the limitations of previous studies.\r\nThe time-evolution shows typical signatures of localization at small densities, replaced by thermal behavior at larger densities.\r\nOur results provide evidence in favor of the stability of many-body mobility edges, which was recently challenged by a theoretical argument.\r\nTo support our findings, we probe the mechanism proposed as a cause of delocalization in many-body localized systems with mobility edges suggesting its ineffectiveness in the model studied.\r\n\r\nIn the last Chapter of this Thesis, we address the topic of many-body localization proximity effect.\r\nWe study a model inspired by recent experiments, featuring Anderson localized coupled to a small bath of free hard-core bosons.\r\nThe interaction among the two particle species results in non-trivial dynamics, which we probe using tensor network techniques.\r\nOur simulations show convincing evidence of many-body localization proximity effect when the bath is composed by a single free particle and interactions are strong.\r\nWe furthter observe an anomalous entanglement dynamics, which we explain through a phenomenological theory.\r\nFinally, we extract highly excited eigenstates of large systems, providing supplementary evidence in favor of our findings.","lang":"eng"}],"department":[{"_id":"GradSch"},{"_id":"MaSe"}],"publication_status":"published","date_published":"2023-03-21T00:00:00Z","date_updated":"2023-09-20T10:44:12Z","tmp":{"legal_code_url":"https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode","short":"CC BY-NC-SA (4.0)","image":"/images/cc_by_nc_sa.png","name":"Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)"},"supervisor":[{"id":"47809E7E-F248-11E8-B48F-1D18A9856A87","full_name":"Serbyn, Maksym","first_name":"Maksym","last_name":"Serbyn","orcid":"0000-0002-2399-5827"}],"month":"03","article_processing_charge":"No","day":"21","degree_awarded":"PhD","license":"https://creativecommons.org/licenses/by-nc-sa/4.0/","type":"dissertation","file":[{"relation":"source_file","checksum":"5d2de651ef9449c1b8dc27148ca74777","content_type":"application/zip","file_name":"Thesis_sub_PBrighi.zip","creator":"pbrighi","access_level":"closed","date_updated":"2023-03-23T16:42:56Z","file_id":"12753","file_size":42167561,"date_created":"2023-03-23T16:42:56Z"},{"access_level":"open_access","creator":"pbrighi","file_name":"Thesis_PBrighi.pdf","content_type":"application/pdf","checksum":"7caa153d4a5b0873a79358787d2dfe1e","relation":"main_file","date_created":"2023-03-23T16:43:14Z","file_size":13977000,"success":1,"file_id":"12754","date_updated":"2023-03-23T16:43:14Z"}],"project":[{"_id":"23841C26-32DE-11EA-91FC-C7463DDC885E","name":"Non-Ergodic Quantum Matter: Universality, Dynamics and Control","grant_number":"850899","call_identifier":"H2020"}],"ddc":["530"],"file_date_updated":"2023-03-23T16:43:14Z","acknowledged_ssus":[{"_id":"ScienComp"}],"year":"2023","_id":"12732","language":[{"iso":"eng"}],"citation":{"ama":"Brighi P. Ergodicity breaking in disordered and kinetically constrained quantum many-body systems. 2023. doi:<a href=\"https://doi.org/10.15479/at:ista:12732\">10.15479/at:ista:12732</a>","ista":"Brighi P. 2023. Ergodicity breaking in disordered and kinetically constrained quantum many-body systems. Institute of Science and Technology Austria.","chicago":"Brighi, Pietro. “Ergodicity Breaking in Disordered and Kinetically Constrained Quantum Many-Body Systems.” Institute of Science and Technology Austria, 2023. <a href=\"https://doi.org/10.15479/at:ista:12732\">https://doi.org/10.15479/at:ista:12732</a>.","apa":"Brighi, P. (2023). <i>Ergodicity breaking in disordered and kinetically constrained quantum many-body systems</i>. Institute of Science and Technology Austria. <a href=\"https://doi.org/10.15479/at:ista:12732\">https://doi.org/10.15479/at:ista:12732</a>","short":"P. Brighi, Ergodicity Breaking in Disordered and Kinetically Constrained Quantum Many-Body Systems, Institute of Science and Technology Austria, 2023.","mla":"Brighi, Pietro. <i>Ergodicity Breaking in Disordered and Kinetically Constrained Quantum Many-Body Systems</i>. Institute of Science and Technology Austria, 2023, doi:<a href=\"https://doi.org/10.15479/at:ista:12732\">10.15479/at:ista:12732</a>.","ieee":"P. Brighi, “Ergodicity breaking in disordered and kinetically constrained quantum many-body systems,” Institute of Science and Technology Austria, 2023."},"ec_funded":1,"publication_identifier":{"issn":["2663-337X"]},"author":[{"full_name":"Brighi, Pietro","id":"4115AF5C-F248-11E8-B48F-1D18A9856A87","first_name":"Pietro","last_name":"Brighi","orcid":"0000-0002-7969-2729"}],"has_accepted_license":"1","doi":"10.15479/at:ista:12732","page":"158"}