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

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.