Disorder-induced excitation continuum in a spin-1/2 cobaltate on a triangular lattice

TL;DR

This study reveals a disorder-induced spin excitation continuum in a triangular-lattice cobaltate, demonstrating how magnetic disorder can mimic quantum spin liquid features in neutron scattering experiments.

Contribution

It provides direct experimental evidence that magnetic disorder can induce a spin excitation continuum in a frustrated quantum magnet, challenging the interpretation of such continua as solely quantum spin liquid signatures.

Findings

Discovered a wave-vector-dependent excitation continuum in CoZnMo₃O₈

The continuum diminishes with increasing temperature

The continuum arises from disorder-induced dynamic spin states

Abstract

A spin-1/2 triangular-lattice antiferromagnet is a prototypical frustrated quantum magnet, which exhibits remarkable quantum many-body effects that arise from the synergy between geometric spin frustration and quantum fluctuations. It can host quantum frustrated magnetic topological phenomena like quantum spin liquid (QSL) states, highlighted by the presence of fractionalized quasiparticles within a continuum of magnetic excitations. In this work, we use neutron scattering to study CoZnMo$_3$O$_8$, which has a triangular lattice of Jeff = 1/2 Co2+ ions with octahedral coordination. We found a wave-vector-dependent excitation continuum at low energy that disappears with increasing temperature. Although these excitations are reminiscent of a spin excitation continuum in a QSL state, their presence in CoZnMo$_3$O$_8$ originates from magnetic intersite disorder-induced dynamic spin states with peculiar excitations. Our results, therefore, give direct experimental evidence for the presence of a disorder-induced spin excitation continuum.