Optical spectral weight distribution in d-wave superconductors

TL;DR

This paper investigates how impurity levels, temperature, and impurity potential influence the distribution of optical spectral weight in d-wave superconductors, revealing residual absorption and the effects of boson interactions.

Contribution

It provides a detailed analysis of spectral weight distribution in d-wave superconductors considering impurities, temperature, and Eliashberg theory effects, highlighting residual absorption at zero temperature.

Findings

Residual absorption persists at T=0 due to impurities.

Spectral weight shifts from the condensate to the infrared.

Incoherent boson-assisted background contributes significantly.

Abstract

The distribution in frequency of optical spectral weight remaining under the real part of the optical conductivity in the superconducting state of a d-wave superconductor depends on impurity concentration, on the strength of the impurity potential as well as on temperature and there is some residual absorption even at T = 0. In BCS theory the important weight is confined to the microwave region if the scattering is sufficiently weak. In an Eliashberg formulation substantial additional weight is to be found in the incoherent, boson assisted background which falls in the infrared and is not significantly depleted by the formation of the condensate, although it is shifted as a result of the opening of a superconducting gap.