Finite-size subthermal regime in disordered SU ( N ) -symmetric Heisenberg chains

Journal Article · 04 March 2024 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.109.094201 · OSTI ID:2406890

Saraidaris, Dimitris  ^[1]; Li, Jheng-Wei  ^[2]; Weichselbaum, Andreas  ^[3]; von Delft, Jan ^[4]; Abanin, Dmitry A. ^[5]

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1. Ludwig Maximilian Univ. of Munich, Munich (Germany); Freie Univ., Berlin (Germany)
2. Ludwig Maximilian Univ. of Munich, Munich (Germany); Univ. of Grenoble Alpes, Grenoble (France)
3. Brookhaven National Laboratory (BNL), Upton, NY (United States)
4. Ludwig Maximilian Univ. of Munich, Munich (Germany)
5. Univ. of Geneva (Switzerland); Princeton Univ., NJ (United States)

SU⁡(N) symmetry is incompatible with the many-body localized (MBL) phase, even when strong disorder is present. However, recent studies have shown that finite-size SU⁡(2) systems exhibit nonergodic, subthermal behavior, characterized by the breakdown of the eigenstate thermalization hypothesis, and by the excited eigenstates entanglement entropy that is intermediate between area and volume law. In this paper, we extend previous studies of the SU⁡(2)-symmetric disordered Heisenberg model to larger systems, using the time-dependent density matrix renormalization group (tDMRG) method. We simulate quench dynamics from weakly entangled initial states up to long times, finding robust subthermal behavior at stronger disorder. Although we find an increased tendency towards thermalization at larger system sizes, the subthermal regime persists at intermediate time scales, nevertheless, and therefore should be accessible experimentally. At weaker disorder, we observe signatures of thermalization; however, entanglement entropy exhibits slow sublinear growth, in contrast to conventional thermalizing systems. Furthermore, we study dynamics of the SU⁡(3)-symmetric disordered Heisenberg model. Similarly, strong disorder drives the system into subthermal regime, albeit thermalizing phase is broader compared to the SU⁡(2) case. Finally, our findings demonstrate the robustness of the subthermal regime in spin chains with non-Abelian continuous symmetry, and are consistent with eventual thermalization at large system sizes and long time scales, suggested by previous studies.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
• Grant/Contract Number: SC0012704
• OSTI ID: 2406890
• Report Number(s): BNL--225841-2024-JAAM
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 9 Vol. 109; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English