Resonant Enhancement of Inelastic Light Scattering in Strongly Correlated Materials

Abstract

We use dynamical mean field theory to find an exact solution for inelastic light scattering in strongly correlated materials such as those near a quantum-critical metal-insulator transition. We evaluate the results for q=0 (Raman) scattering and find that resonant effects can be quite large, and yield a double resonance, a significant enhancement of nonresonant scattering peaks, a joint resonance of both peaks when the incident photon frequency is on the order of U, and the appearance of an isosbestic point in all symmetry channels for an intermediate range of incident photon frequencies.

Nonlinear light–Higgs coupling in superconductors beyond BCS: Effects of the retarded phonon-mediated interaction

“…Indeed, it has been shown in the study of Raman scattering for correlated electron systems that the resonant contribution can significantly enhance the non-resonant Raman response. 61,62 This has motivated us to study here the nonlinear optical response of superconductors for electron-phonon coupled systems beyond the BCS approximation. Theoretically, it is quite challenging to evaluate all of the non-resonant, mixed and resonant diagrams involving the four-point vertex on an equal footing, since the vertex carries three independent momenta and frequencies.…”

“…In higher dimensions in the thermodynamic limit, an analysis including the vertex correction has so far been performed only in exceptional cases, such as the Raman response of the Falicov-Kimball model. 61,62,64,65 For the Hubbard model, the nonlinear optical response has been analyzed by HartreeFock approximation, 66 by DMFT without considering vertex corrections, 67,68 and by exact diagonalization for small finitesize systems. 69,70 For the Holstein model, higher-harmonic generation has been studied by Migdal approximation without considering vertex corrections.…”

Raman Light Scattering in Pseudospin-Electron Model at Strong Pseudospin-Electron Interaction

“…It should be noted that in contrast to other methods of Raman spectra investigations [5], in our approach many-time correlation functions do not appear; this fact essentially simplifies the calculation.…”

“…Raman spectra are also investigated for normal (nonsuperconducting) state for the cases of metals and dielectrics [2][3][4]. Resonance, nonresonance and mixed contributions to Raman spectra are studied [3][4][5].…”

“…In this work we calculate Raman spectra for the system described by the pseudospin-electron model (PEM) using the method which is based on the construction of a polarizability operatorP in the framework of a microscopic approach; the method was developed in [6][7][8][9] and is an alternative to standard ones [2][3][4][5]. PEM describes the systems with locally anharmonic elements (anharmonic vibrations of apical oxygen O4 in HTSC of YBaCuO-type, the systems with hydrogen bonds, etc.).…”