Low temperature quasiparticle transport in a d-wave superconductor with coexisting charge order

TL;DR

This paper studies how charge order affects quasiparticle excitations and heat transport in a d-wave superconductor, revealing a transition to a fully gapped spectrum and vanishing thermal conductivity at a critical charge order strength.

Contribution

It provides a theoretical analysis of the impact of charge density wave order on quasiparticle spectra and thermal transport in d-wave superconductors, including analytical expressions and numerical results.

Findings

Quasiparticle nodes survive charge order up to a critical point.

Thermal conductivity decreases and vanishes at the transition to a fully gapped spectrum.

Analytical formulas derived for isotropic Dirac nodes in the clean limit.

Abstract

In light of the evidence that charge order coexists with d-wave superconductivity in the underdoped cuprate superconductors, we investigate the manner in which such charge order will influence the quasiparticle excitations of the system and, in particular, the low-temperature transport of heat by those quasiparticles. We consider a d-wave superconductor in which the superconductivity coexists with charge density wave order of wave vector (\pi/a,0). While the nodes of the quasiparticle energy spectrum survive the onset of charge order, there exists a critical value of the charge density wave order parameter beyond which the quasiparticle spectrum becomes fully gapped. We perform a linear response Kubo formula calculation of thermal conductivity in the low temperature (universal) limit. Results reveal the dependence of thermal transport on increasing charge order up to the critical value at which the quasiparticle spectrum becomes fully gapped and thermal conductivity vanishes. In addition to numerical results, closed-form expressions are obtained in the clean limit for the special case of isotropic Dirac nodes. Signatures of the influence of charge order on low-temperature thermal transport are identified.