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Absence of thermalization after a local quench and strong violation of the eigenstate thermalization hypothesis

Peter Reimann and Christian Eidecker-Dunkel

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Phys. Rev. B 113, 144304 – Published 6 April, 2026

DOI: https://doi.org/10.1103/zp5y-6d5w

Abstract

Absence of thermalization after a global quantum quench is a well-established numerical observation in integrable many-body systems, and can be empirically related to a violation of the eigenstate thermalization hypothesis (ETH) in such models. Still, in many of those examples, a weaker version of the conventional ETH (wETH) has been numerically reported or even rigorously proven. In this paper, we show analytically and illustrate numerically that the absence of thermalization is already possible after a local quench. A closely related finding is a strong violation of the ETH, meaning that not even the wETH is fulfilled anymore. In our analytical explorations, we focus on XX-spin-chain models with open boundary conditions, where the local quench is generated by initiating the system in thermal equilibrium and then suddenly switching on (or slightly changing) a single-spin impurity either at the end or in the center of the chain. Numerically, we observe qualitatively similar phenomena also for more general XXZ models in the case of an end-impurity, but not in the case of a central impurity.

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Phys. Rev. B 113, 144304– Published 6 April, 2026
  • Received 23 July 2025
  • Revised 4 March 2026
  • Accepted 18 March 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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