On the Relation between Optical Conductivity and Quasiparticle Dynamics: Boson Structures

TL;DR

This paper explores the connection between optical conductivity and quasiparticle dynamics, introducing a new model scattering rate that better relates to the self energy, especially in the normal state, and discusses limitations in the superconducting state.

Contribution

It introduces a new auxiliary model scattering rate derived from optical data that more accurately reflects the quasiparticle self energy in isotropic systems.

Findings

The auxiliary scattering rate closely matches the quasiparticle self energy in the normal state.

The simplification breaks down in the superconducting state due to energy-dependent density of states.

The study emphasizes the importance of boson signatures in optical and quasiparticle analyses.

Abstract

An extended Drude form is often used to analyze optical data in terms of an optical scattering rate and renormalized mass corresponding, respectively, to the real and imaginary part of the memory function. We study the relationship between memory function and quasiparticle self energy for an isotropic system. We emphasize particularly boson signatures. We find it useful to introduce a new auxiliary model scattering rate and its Kramers-Kronig transform determined solely from optics which are much closer to the self energy than is the memory function itself in the normal state. In the superconducting state the simplification fails because the quasiparticle density of states acquires an essential energy dependence.