How to detect weak emergent broken-symmetries of the Kagome antiferromagnet from Raman spectroscopy

TL;DR

This paper proposes a Raman spectroscopy method to detect weak broken symmetries and emergent order parameters in Kagome antiferromagnets, distinguishing spin-liquid states from valence bond crystals.

Contribution

It introduces a way to identify broken symmetries in Kagome antiferromagnets through polarization-dependent Raman response analysis.

Findings

Raman response of spin-liquid is polarization-independent.

Broken symmetry states show characteristic polarization oscillations.

Method can differentiate between spin-liquid and valence bond crystal states.

Abstract

We show that the magnetic Raman response of a spin-liquid is independent of the polarizations of the light for triangular symmetries. In contrast, a ground-state that has a broken symmetry shows characteristic oscillations when the polarizations are rotated. This would allow to detect weak broken symmetries and emergent order-parameters. We focus on the Kagome antiferromagnet where no conventional long-range order has been found so far, and present the Raman cross-section of a spin-liquid and a valence bond crystal (VBC) using a random phase approximation.