Raman Scattering Signatures of Kitaev Spin Liquids in A$_2$ IrO$_3$ Iridates

TL;DR

This paper theoretically analyzes the Raman scattering response in Kitaev spin liquids, revealing how emergent Majorana fermions and flux excitations influence the spectral features, with implications for experimental detection.

Contribution

It introduces a detailed theoretical framework for Raman response in Kitaev spin liquids, accounting for integrability-breaking effects and flux excitations, advancing understanding of experimental signatures.

Findings

Raman response reflects Majorana fermion density of states

Flux excitations produce a sharp peak and broad features in spectra

Integrability-breaking modifies the polarization dependence of the response

Abstract

We study theoretically the Raman scattering response $I(\omega)$ in the gapless quantum spin liquid phase of the Kitaev-Heisenberg model. The dominant polarization-independent contribution $I_K (\omega)$ reflects the density of states of the emergent Majorana fermions in the ground-state flux-sector. The integrability-breaking Heisenberg exchange generates a second contribution, whose dominant part $I_H (\omega)$ has the form of a quantum quench corresponding to an abrupt insertion of four $Z_2$ gauge fluxes. This results in a weakly polarization dependent response with a sharp peak at the energy of the flux excitation accompanied by broad features, which can be related to Majorana fermions in the presence of the perturbed gauge field. We discuss the experimental situation and explore more generally the influence of integrability breaking for Kitaev spin liquid response functions.