Optical conductivity of overdoped cuprate superconductors: application to LSCO

TL;DR

This paper explains the optical conductivity and superfluid density in overdoped LSCO cuprates using disordered BCS d-wave theory, highlighting the role of weak scatterers and disorder in suppressing superconductivity.

Contribution

It demonstrates that the optical properties of overdoped LSCO can be understood within a disordered BCS d-wave framework, emphasizing the impact of weak scatterers and disorder.

Findings

Large scattering rates are due to weak scatterers like Sr dopants.

Overdoped cuprates approach BCS weak-coupling behavior.

Disorder significantly contributes to the suppression of T_c.

Abstract

We argue that recent measurements on both the superfluid density and the optical conductivity of high-quality LSCO films can be understood almost entirely within the theory of disordered BCS d-wave superconductors. The large scattering rates deduced from experiments are shown to arise predominantly from weak scatterers, probably the Sr dopants out of the CuO$_2$ plane, and correspond to significant suppression of $T_c$ relative to a pure reference state with the same doping. Our results confirm the "conventional" viewpoint that the overdoped side of the cuprate phase diagram can be viewed as approaching the BCS weak-coupling description of the superconducting state, with significant many-body renormalization of the plasma frequency. They suggest that, while some of the decrease in $T_c$ with overdoping may be due to weakening of the pairing, disorder plays an essential role.