Impurity effects in unconventional density waves in the unitary limit

TL;DR

This paper studies how strong nonmagnetic impurities affect unconventional density waves, revealing similarities to d-wave superconductors and identifying unique optical conductivity features.

Contribution

It demonstrates that in the unitary limit, UDW thermodynamics mirror those of d-wave superconductors and explores impurity-induced optical conductivity structures.

Findings

UDW thermodynamics match d-wave superconductor behavior in the unitary limit

Optical conductivity shows new structures related to impurity bound states

Universal electric conductivity is observed in the dc limit

Abstract

We investigate the effect of strong, nonmagnetic impurities on quasi-one-dimensional conventional and unconventional density waves (DW and UDW). The conventional case remains unaffected similarly to s-wave superconductors in the presence of weak, nonmagnetic impurities. The thermodynamic properties of UDW were found to be identical to those of a d-wave superconductor in the unitary limit. The real and imaginary part of the optical conductivity is determined for electric fields applied in the perpendicular directions. A new structure can be present corresponding to excitations from the bound state at the Fermi energy to the gap maximum in addition to the usual peak at 2\Delta. In the dc limit, universal electric conductivity is found.