Chaos enhancement in large-spin chains

TL;DR

This paper investigates how increasing spin size in a disordered XXZ chain affects quantum chaos, finding that added decay channels can restore chaos suppressed by large spins.

Contribution

It reveals that large spins suppress quantum chaos in disordered chains and proposes a method using decay channels to reintroduce chaotic behavior.

Findings

Large spins reduce quantum chaos features.

Decay channels restore chaos in large-spin chains.

Only three excitations needed for ergodic eigenstates.

Abstract

We study the chaotic properties of a large-spin XXZ chain with onsite disorder and a small number of excitations above the fully polarized state. We show that while the classical limit, which is reached for large spins, is chaotic, enlarging the spin suppresses quantum chaos features. We attribute this suppression to the occurrence of large and slow clusters of onsite excitations, and propose a way to facilitate their fragmentation by introducing additional decay channels. We numerically verify that the introduction of such relaxation channels restores chaoticity for large spins, so that only three excitations are required to achieve strong level repulsion and ergodic eigenstates.