Raman scattering in a Heisenberg $S=\frac{1}{2}$ antiferromagnet on the anisotropic triangular lattice

We investigate the two-magnon Raman scattering from an anisotropic $S=\frac{1}{2}$ triangular Heisenberg antiferromagnet Cs${}_2$CuCl${}_4$. We find that the Raman response is very sensitive to magnon-magnon interactions and to scattering geometries, a feature that is in remarkable contrast with the polarization-independent Raman signal from the isotropic triangular Heisenberg antiferromagnet. Since a spin-liquid ground state gives rise to a similar rotationally invariant Raman response, our results on the polarization dependence of the scattering spectrum suggest that Raman spectroscopy provides a useful probe, complementary to neutron scattering, of the ground-state properties of Cs${}_2$CuCl${}_4$, particularly whether the time-reversal symmetry is broken in the ground state.