Quantum spin liquids are long-range entangled states of matter with emergent gauge fields and fractionalized excitations. While candidate materials, such as the Kitaev honeycomb ruthenate α-RuCl3, show magnetic order at low temperatures T, here we demonstrate numerically a dynamical crossover from magnonlike behavior at low T and frequencies ω to long-lived fractionalized fermionic quasiparticles at higher T and ω. This crossover is akin to the presence of spinon continua in quasi-1D spin chains. It is further shown to go hand in hand with persistent typicality down to very low T. This aspect, which has also been observed in the spin-1/2 kagome Heisenberg antiferromagnet, is a signature of proximate spin liquidity and emergent gauge degrees of freedom more generally, and can be the basis for the numerical study of many finite-T properties of putative spin liquids.
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We thank W. Brenig, K. Burch, M. Daghofer, A. Honecker and X. Zotos for fruitful discussions. I.R. acknowledges the hospitality of the Max Planck Institute for the Physics of Complex Systems (MPI-PKS) of Dresden, where part of this work was done. This work was in part supported by the Deutsche Forschungsgemeinschaft via Grant No. SFB 1143. S.K. was partially supported through the Boston University Center for Non-Equilibrium Systems and Computation. I.R. and N.B.P. were supported by the US Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0018056.
© 2019 American Physical Society.