Quantum Beats in Many-Body Localized Systems

Bernard Faulend; Hrvoje Buljan; Antonio Štrkalj

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arXiv · 2603.28721

Quantum Beats in Many-Body Localized Systems

Bernard Faulend·Hrvoje Buljan·Antonio Štrkalj

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Abstract

Slow particle dynamics observed numerically even deep inside the many-body localized (MBL) regime has called the stability of MBL in the thermodynamic limit into question, and its microscopic origin remains unknown. Here, we show that this slow dynamics originates from many-body quantum beats that arise from the interaction-induced modulation of oscillations associated with single-particle hopping processes. We relate this mechanism to local integrals of motion (LIOMs) and show that it survives at arbitrarily large distances between LIOMs, is consistent with the stability of MBL in the thermodynamic limit, and is generic to many-body systems. We present new numerical results for quasiperiodic potentials and, based on the quantum beats mechanism, develop an analytical model that explains number entropy growth and quasiparticle spreading, as well as clarifies the distinct MBL phenomenology observed in quasiperiodic and random potentials. Lastly, we propose concrete signatures for observing many-body quantum beats in existing experimental platforms.

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Bernard Faulend, Hrvoje Buljan, Antonio Štrkalj. 2026-07-20. Quantum Beats in Many-Body Localized Systems. https://arxiv.org/abs/2603.28721

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