Integrability of a disordered Heisenberg spin-1/2 chain

TL;DR

This paper explores how introducing defects in a Heisenberg spin-1/2 chain affects its transition from integrability to chaos, showing that even a single defect can induce quantum chaos.

Contribution

It demonstrates that the presence of a defect, rather than randomness, causes the transition to quantum chaos in the Heisenberg spin-1/2 chain.

Findings

Single defects induce quantum chaos.

Random distribution of defects leads to chaos.

Chaos can occur with a single defect at the edge.

Abstract

We investigate how the transition from integrability to nonintegrability occurs by changing the parameters of the Hamiltonian of a Heisenberg spin-1/2 chain with defects. Randomly distributed defects may lead to quantum chaos. A similar behavior is obtained in the presence of a single defect out of the edges of the chain, suggesting that randomness is not the cause of chaos in these systems, but the mere presence of a defect.