Decay of quasiparticles in quantum spin liquids

TL;DR

This paper investigates how quasiparticles decay in gapped quantum spin liquids, revealing nonanalytic behaviors and suppression effects in different dimensions, with implications for understanding magnetic excitations.

Contribution

It provides a detailed analysis of quasiparticle decay mechanisms in quantum spin liquids, including momentum dependence and external field effects, which were not fully understood before.

Findings

Nonanalytic frequency and momentum dependence near two-magnon continuum boundary

Termination point of single-particle branch in 1D systems

Strong suppression of quasiparticle weight in 2D systems

Abstract

Magnetic excitations are studied in gapped quantum spin systems, for which spontaneous two-magnon decays are allowed by symmetry. Interaction between one- and two-particle states acquires nonanalytic frequency and momentum dependence near the boundary of two-magnon continuum. This leads to a termination point of single-particle branch for one-dimensional systems and to strong suppression of quasiparticle weight in two dimensions. The momentum dependence of the decay rate is calculated in arbitrary dimensions and effect of external magnetic field is discussed.