Thermalization of Quantum Many-Body Scars in Kinetically Constrained Systems

TL;DR

This paper extends the eigenstate thermalization hypothesis (ETH) to include quantum many-body scars (QMBS) within a grand canonical framework, unifying non-ergodic and thermal states through a dissipative open system approach.

Contribution

It introduces a new grand canonical ETH formulation for QMBS, linking their slow decay to thermalization in open systems, and unifies scar and thermal states under a common thermodynamic description.

Findings

Reformulation of ETH for open quantum systems.

Demonstration that scars thermalize under grand canonical statistics.

Resolution of the tension between non-ergodicity and thermalization.

Abstract

The phenomenon of quantum many-body scars (QMBS) has been studied both theoretically and experimentally, due to its unusual violation of the eigenstate thermalization hypothesis (ETH). In this paper, we extend the ETH to a new description based on the grand canonical ensemble to depict the thermal properties of QMBS models. For this purpose, we embed the dynamics of kinetically constrained systems within the Lindblad-like master equation, and demonstrate that the violation of the ETH by scar eigenstates is related to their slow decay in the corresponding dissipative process. Within this open system description, we reformulate the ETH to demonstrate that both scar eigenstates and thermal ones exhibit thermalization governed by grand canonical statistics. Consequently, our revised ETH unifies scars and thermal states under a cohesive thermodynamic rule. Our work resolves the fundamental tension between constraint-induced non-ergodicity and thermalization paradigms, establishing a unified route to generalized thermalization for quantum many-body systems.