Selfconsistent gauge-invariant theory of in-plane infrared response of high-Tc cuprate superconductors involving spin fluctuations

TL;DR

This paper presents a gauge-invariant theoretical model for the in-plane infrared response of high-Tc cuprate superconductors, emphasizing the role of spin fluctuations and vertex corrections in explaining spectral features.

Contribution

It introduces a self-consistent, gauge-invariant approach incorporating vertex corrections to better understand infrared spectra of cuprates.

Findings

Increased intraband optical spectral weight due to vertex corrections

Transfer of spectral weight from far to mid infrared

Reduced spectral weight of the superconducting condensate

Abstract

We report on results of our theoretical study of the in-plane infrared conductivity of the high-Tc cuprate superconductors using the model where charged planar quasiparticles are coupled to spin fluctuations. The computations include both the renormalization of the quasiparticles and the corresponding modification of the current-current vertex function (vertex correction), which ensures gauge invariance of the theory and local charge conservation in the system. The incorporation of the vertex corrections leads to an increase of the total intraband optical spectral weight (SW) at finite frequencies, a SW transfer from far infrared to mid infrared, a significant reduction of the SW of the superconducting condensate, and an amplification of characteristic features in the superconducting state spectra of the inverse scattering rate 1/tau. We also discuss the role of selfconsistency and propose a new interpretation of a kink occurring in the experimental low temperature spectra of 1/tau around 1000cm^{-1}.