Electronic Raman scattering in unconventional density waves

TL;DR

This paper develops a theoretical framework for electronic Raman scattering in unconventional density wave states, revealing polarization-dependent spectral features and collective mode effects in quasi-one-dimensional conductors.

Contribution

It provides a comprehensive mean-field and RPA-level analysis of Raman response in unconventional density waves, including collective modes and Coulomb screening effects.

Findings

Raman spectra are finite in the gapped low-temperature phase and vanish in the normal state.

Distinct lineshapes depend on scattering geometry and the density wave order parameter.

Unconventional density waves show characteristic polarization-dependent spectral features.

Abstract

We investigate the electronic Raman scattering in pure, quasi-one dimensional conductors with density wave ground state. In particular, we develop the theory of light-scattering on spin and charge density waves, both conventional and unconventional. We calculate the electronic Raman response of the interacting electron system with a single, highly anisotropic conduction band. The calculation is carried out in the mean field approximation. Beside the quasiparticle contribution, the electron-electron interaction is also included on RPA level. The contribution of collective modes and the effect of Coulomb screening are investigated. In analogy with unconventional superconductivity, the obtained Raman spectra - which are finite in the low temperature phase possessing a gap, and vanish identically in the normal state - show unique and strong dependence on the polarization of the incoming and scattered light. We have found distinct, characteristic lineshapes, especially in the unconventional situation, depending on the various scattering geometries and the particular momentum dependence of the density wave order parameter.