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

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.

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Publication Details

Journal
Physical Review Research
Published
2025-09-12
DOI
https://doi.org/10.1103/crwj-x7j8
Citations
1
Primary Topic
Quantum many-body systems
Type
article
Field-Weighted Citation Impact
1.25
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article

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

Federico Balducci, Pietro Brighi, Federico Roccati, Marko Ljubotina
1 citations
Physical Review Research
Quantum many-body systems
1.25
article

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

Federico Balducci, Pietro Brighi, Federico Roccati, Marko Ljubotina
article en
1 citations

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.

Physical Review ResearchVol. 7(4)
University of Vienna (AT), Institute of Science and Technology Austria (AT), Max Planck Institute for the Science of Light (DE), Max Planck Institute for the Physics of Complex Systems (DE), Industriale Chimica (Italy) (IT), Munich Center for Quantum Science and Technology (DE), Technical University of Munich (DE), University of Palermo (IT)
Openalex Percentile: Top 17%
Quantum many-body systems
1.25
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