Quasiparticles in quantum spin chains with long-range interactions

TL;DR

This paper investigates quasiparticle excitations in quantum spin chains with long-range interactions using variational matrix product state methods, revealing accurate modeling of excitations, the breaking of Lieb-Robinson bounds, and quasiparticle crossover phenomena.

Contribution

It introduces a variational matrix product state approach to accurately analyze quasiparticles in long-range interacting spin chains, including topological excitations.

Findings

Local quasiparticle ansatz accurately captures excitations.

Breaking of Lieb-Robinson bound linked to dispersion cusps.

Crossover between different quasiparticles observed with interaction tuning.

Abstract

We study quasiparticle excitations for quantum spin chains with long-range interactions using variational matrix product state techniques. It is confirmed that the local quasiparticle ansatz is able to capture those excitations very accurately, even when the correlation length becomes very large and in the case of topological nontrivial excitation such as spinons. It is demonstrated that the breaking of the Lieb-Robinson bound follows from the appearance of cusps in the dispersion relation, and evidence is given for a crossover between different quasiparticles as the long-range interactions are tuned.