Optical phonons coupled to a Kitaev spin liquid

Abstract

Emergent excitation continua in frustrated magnets are a fingerprint of fractionalization, characteristic of quantum spin-liquid states. Recent evidence from Raman scattering for a coupling between such continua and lattice degrees of freedom in putative Kitaev magnets [1-6] may provide insight into the nature of the fractionalized quasiparticles. Here we study the renormalization of optical phonons coupled to the underlying ${\mathbb{Z}}_2$ quantum spin-liquid. We show that phonon line-shapes acquire an asymmetry, observable in light scattering, and originating from two distinct sources, namely the dispersion of the Majorana continuum and the Fano effect. Moreover, we find that the phonon life-times increase with increasing temperature due to thermal blocking of available phase space. Finally, in contrast to low-energy probes, optical phonon renormalization is rather insensitive to thermally excited gauge fluxes and barely susceptible to external magnetic fields.

arXiv comment6 pages, 3 figures

Cited by in corpus (4)

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• Thermal Hall Effect in the Kitaev-Heisenberg System with Spin-Phonon Coupling
• Footprints of the Kitaev spin liquid in the Fano lineshapes of the Raman active optical phonons
• Signatures of non-Loudon-Fleury Raman scattering in the Kitaev magnet $\beta$-Li${}_2$IrO${}_3$