Finite steady-state current defies non-Hermitian many-body localization

Brighi P, Ljubotina M, Roccati F, Balducci F. 2025. Finite steady-state current defies non-Hermitian many-body localization. Physical Review Research. 7(4), L042014.

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Author
Brighi, PietroISTA ; Ljubotina, MarkoISTA ; Roccati, Federico; Balducci, Federico
Department
Abstract
Non-Hermitian many-body localization (NH MBL) has emerged as a possible scenario for stable localization in open systems, as suggested by spectral indicators identifying a putative transition for finite system sizes. In this work, we shift the focus to dynamical probes, specifically the steady-state spin current, to investigate transport properties in a disordered, non-Hermitian XXZ spin chain. Through exact diagonalization for small systems and tensor-network methods for larger chains, we demonstrate that the steady-state current remains finite and decays exponentially with disorder strength, showing no evidence of a transition up to disorder values far beyond the previously claimed critical point. Our results reveal a stark discrepancy between spectral indicators, which suggest localization, and transport behavior, which indicates delocalization. This highlights the importance of dynamical observables in characterizing NH MBL and suggests that traditional spectral measures may not fully capture the physics of non-Hermitian systems. Additionally, we observe a noncommutativity of limits in system size and time, further complicating the interpretation of finite-size studies. These findings challenge the existence of NH MBL in the studied model and underscore the need for alternative approaches to understanding localization in non-Hermitian settings.
Publishing Year
Date Published
2025-10-01
Journal Title
Physical Review Research
Publisher
American Physical Society
Acknowledgement
F.B. thanks Giuseppe de Tomasi and Oskar A. Prośniak for discussion. P.B. acknowledges support by the Austrian Science Fund (FWF) (Grant Agreement No. 10.55776/ESP9057324). This research was funded in whole or in part by the Austrian Science Fund (FWF) [10.55776/COE1]. The numerical simulations were performed using the ITensor library [73] on the Vienna Scientific Cluster (VSC) and on the MPIPKS HPC cluster. M.L. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy—EXC-2111—390814868. F.R. acknowledges support by the European Union-Next Generation EU with the project “Quantum Optics in Many-Body photonic Environments” (QOMBE) code SOE2024_0000084-CUP B77G24000480006. Open access publication funded by Max Planck Society.
Volume
7
Issue
4
Article Number
L042014
eISSN
IST-REx-ID

Cite this

Brighi P, Ljubotina M, Roccati F, Balducci F. Finite steady-state current defies non-Hermitian many-body localization. Physical Review Research. 2025;7(4). doi:10.1103/crwj-x7j8
Brighi, P., Ljubotina, M., Roccati, F., & Balducci, F. (2025). Finite steady-state current defies non-Hermitian many-body localization. Physical Review Research. American Physical Society. https://doi.org/10.1103/crwj-x7j8
Brighi, Pietro, Marko Ljubotina, Federico Roccati, and Federico Balducci. “Finite Steady-State Current Defies Non-Hermitian Many-Body Localization.” Physical Review Research. American Physical Society, 2025. https://doi.org/10.1103/crwj-x7j8.
P. Brighi, M. Ljubotina, F. Roccati, and F. Balducci, “Finite steady-state current defies non-Hermitian many-body localization,” Physical Review Research, vol. 7, no. 4. American Physical Society, 2025.
Brighi P, Ljubotina M, Roccati F, Balducci F. 2025. Finite steady-state current defies non-Hermitian many-body localization. Physical Review Research. 7(4), L042014.
Brighi, Pietro, et al. “Finite Steady-State Current Defies Non-Hermitian Many-Body Localization.” Physical Review Research, vol. 7, no. 4, L042014, American Physical Society, 2025, doi:10.1103/crwj-x7j8.
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2025-12-01
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