Exact many-body scars based on pairs or multimers in a chain of spinless fermions

TL;DR

This paper constructs a 1D spinless fermion model featuring exact many-body scar states based on pairs and multimers, which exhibit non-thermal behavior and periodic dynamics, challenging typical thermalization in quantum systems.

Contribution

The authors introduce a new 1D fermionic model with exact many-body scars derived from $ ext{eta}$-pairing states and multimers, expanding understanding of non-thermal eigenstates.

Findings

Scar states form an equally spaced energy tower

Scar states exhibit subvolume entanglement entropy scaling

Model shows periodic oscillations in Loschmidt echo and observables

Abstract

We construct a 1D model Hamiltonian of spinless fermions for which the spinless analogue of $\eta$-pairing states are quantum many-body scars of the model. These states are excited states and display subvolume entanglement entropy scaling; they form a tower of states that are equally spaced in energy (resulting in periodic oscillations in the Loschmidt echo and in the time evolution of observables for initial states prepared in a superposition of them) and are atypical in the sense that they weakly break the eigenstate thermalization hypothesis, while the other excited states are thermal. We extend the approach by presenting models with a tower of scar states generated by multimers located at the edge of the Brillouin zone.