# Weak Ergodicity Breaking and Quantum Many-Body Scars in Spin-1 XY Magnets

## TL;DR

This paper demonstrates that the spin-1 XY model contains special eigenstates called quantum many-body scars, which cause weak ergodicity breaking and persistent oscillations, challenging typical thermalization expectations in nonintegrable systems.

## Contribution

It analytically identifies and characterizes quantum many-body scars in the spin-1 XY model, revealing their properties and implications for ergodicity breaking.

## Key findings

- Existence of anomalous eigenstates with subextensive entanglement
- Persistent oscillations in local observables after quantum quenches
- Analytical understanding of the microscopic origin of scars

## Abstract

We study the spin-1 XY model on a hypercubic lattice in $d$ dimensions and show that this well-known nonintegrable model hosts an extensive set of anomalous finite-energy-density eigenstates with remarkable properties. Namely, they exhibit subextensive entanglement entropy and spatiotemporal long-range order, both believed to be impossible in typical highly excited eigenstates of nonintegrable quantum many-body systems. While generic initial states are expected to thermalize, we show analytically that the eigenstates we construct lead to weak ergodicity breaking in the form of persistent oscillations of local observables following certain quantum quenches--in other words, these eigenstates provide an archetypal example of so-called "quantum many-body scars." This work opens the door to the analytical study of the microscopic origin, dynamical signatures, and stability of such phenomena.