Excitations in a quantum spin liquid with random bonds

TL;DR

This study investigates how bond disorder affects excitations in a quantum spin liquid, revealing increased spin gap, reduced magnon bandwidth, and enhanced damping with disorder.

Contribution

It provides experimental insights into the effects of bond disorder on magnetic excitations in quantum spin liquids using neutron scattering.

Findings

Spin gap increases with bond disorder

Magnon bandwidth decreases with disorder

Magnon damping is enhanced at higher energies

Abstract

We present results of inelastic neutron scattering study on two bond disordered quasi twodimensional quantum magnets (C$_4$H$_12$N$_2$)Cu$_2$(Cl$_{1-x}$Br$_x$)$_6$ with x=0.035 and 0.075. We observe the increase of spin gap, reduction of magnon bandwidth and a decrease of magnon lifetimes compared to x=0 sample. Additional magnon damping is observed at higher energies away from zone center which is found to follow the density of single particle states.