Quantum Many-Body Scars and Quantum Criticality

TL;DR

This paper explores the relationship between quantum many-body scar states and quantum criticality in the PXP Hamiltonian with an external magnetic field, revealing connections that impact thermalization and can be tested experimentally.

Contribution

It uncovers a link between scar states and quantum critical states, showing how scar states relate to Fermi sea states and how thermalization violations diminish near criticality.

Findings

Scar states can be connected to quantum critical states with Fermi sea characteristics.

Partial thermalization violation reduces in the quantum critical regime.

Connections are experimentally verifiable in cold atom platforms.

Abstract

In this letter, we study the PXP Hamiltonian with an external magnetic field that exhibits both quantum scar states and quantum criticality. It is known that this model hosts a series of quantum many-body scar states violating quantum thermalization at zero magnetic field, and it also exhibits an Ising quantum phase transition driven by finite magnetic field. Although the former involves the properties of generic excited states and the latter concerns the low-energy physics, we discover two surprising connections between them, inspired by the observation that both states possess log-volume law entanglement entropies. First, we show that the quantum many-body scar states can be tracked to a set of quantum critical states, whose nature can be understood as pair-wisely occupied Fermi sea states. Second, we show that the partial violation of quantum thermalization diminishes in the quantum critical regime. We envision that these connections can be extended to general situations and readily verified in existing cold atom experimental platforms.