Strong-coupling theory of electronic Raman scattering in high-temperature superconductors

We have calculated the response function for electronic Raman scattering within the fluctuation-exchange approximation for the two-dimensional Hubbard model. Below T-c. a large pair-breaking peak and a gap develop in the B-1g spectrum while the effect of superconductivity on the B-2g spectrum is much smaller, In order to investigate the underdoped regime we study the influence of a phenomenologically introduced pseudogap. In the normal state we find that this pseudogap leads for decreasing temperature to development of a d-wave gap structure in the density of states which merges continuously into the superconducting spectrum. A corresponding pair-breaking peak evolves continuously in the B-1g Raman spectrum as T decreases in the normal state and below T-c. We discuss our results in connection with recent tunneling, optical conductivity, and Raman data on the cuprates. [S0163-1829(99)13721-4].