Schwinger–Keldysh canonical formalism for electronic Raman scattering

摘要: Abstract Inelastic low-energy Raman and high-energy X-ray scatterings have made great progress in instrumentation to investigate the strong electronic correlations matter. However, theoretical study of relevant scattering spectrum is still a challenge. In this paper, we present Schwinger–Keldysh canonical perturbation formalism for scattering, where all resonant, non-resonant mixed responses are considered uniformly. We show how use evaluate cross section off an one-band superconductor. All two-photon processes from electrons, charge density response, elastic Rayleigh fluorescence, intrinsic energy-shift included. mean-field superconducting state, Cooper pairs contribute only response. other dominated by single-particle excitations strongly suppressed due opening gap. Our can be easily extended resonant inelastic scattering.