PUB - Publikationen an der Universität Bielefeld

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.