Anisotropic Thermal Transport in Superconductors with Coexisting Spin Density Waves

Abstract

Thermal conductivity measurements can provide key and experimentally verifiable insight into the electronic transport of unconventional superconductors. In this work, electronic thermal transport of two-dimensional tight-binding metallic systems with coexisting $d$-wave superconducting (SC) and antiferromagnetic spin density wave (SDW) orders with nesting vector $\mathbf{Q} = (\pi/2,\pi/2)$ or $(\pi,0)$ are considered. The coexisting SC and SDW orders are modelled at the mean-field level. Thermal conductivities are numerically calculated within Boltzmann kinetic theory in the weak impurity scattering (Born) limit. These SDW nesting vectors are chosen for their unique property of reconstructing the Fermi surface (FS) parallel to $\mathbf{Q}$ and preserving the metallic FS perpendicular to $\mathbf{Q}$. This leads to anisotropic electronic thermal conductivities parallel and perpendicular to $\mathbf{Q}$, which also depend on the presence or absence of additional gapless excitations exclusive to the coexistence phase. It was found that the $\mathbf{Q} = (\pi/2,\pi/2)$ and $(\pi,0)$ SDW systems exhibit equivalent electron transport relative to $\mathbf{Q}$. These systems also had equivalent electron transport when coexisting with a $d$-wave SC gap when $\Delta_{\mathbf{k}}$ had the same symmetry class under translations of $\mathbf{Q}$.