Role of Symmetry in Raman Spectroscopy of Unconventional Superconductors

The role of symmetry of the inelastic light scattering amplitude, the superconducting energy gap, and the underlying Fermi surface manifold on the Raman spectra of unconventional superconductors is discussed in detail. Particular emphasis is placed on both single and bi-layer superconductors. It is found that the $B_{1g}$ channel may be the most sensitive to doping due to the role of the Van Hove singularity. Lastly the effects of both disorder and spin fluctuations are considered. The theory imposes strong constraints on both the magnitude and symmetry of the energy gap for the bi-layer cuprates, indicating that a nearly identical energy gap of $d_{x^{2}-y^{2}}$ symmetry provides a best fit to the data.