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 such as 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 ${\mathrm{CoZnMo}}_3{\mathrm{O}}_8$, which has a triangular lattice of $J_{\mathrm{eff}}=1/2{\mathrm{Co}}^{2+}$ 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 ${\mathrm{CoZnMo}}_3{\mathrm{O}}_8$ originates from magnetic intersite disorder-induced dynamic spin states with peculiar excitations. Our results, therefore, provide direct experimental evidence for the presence of a disorder-induced spin excitation continuum.

• Received 28 July 2022
• Revised 14 June 2023
• Accepted 7 July 2023

DOI:https://doi.org/10.1103/PhysRevB.108.024431