Unconventional superconductors under a rotating magnetic field. II. Thermal transport

We present a microscopic approach to the calculations of thermal conductivity in unconventional superconductors for a wide range of temperatures and magnetic fields. Our work employs the nonequilibrium Keldysh formulation of the quasiclassical theory. We solve the transport equations using a variation of the BrandtPesch-Tewordt method that accounts for the quasiparticle scattering on vortices. We focus on the dependence of the thermal conductivity on the direction of the field with the respect to the nodes of the order parameter, and discuss it in the context of experiments aiming to determine the shape of the gap from such anisotropy measurements. We consider quasi-two-dimensional Fermi surfaces with vertical line nodes and use our analysis to establish the location of gap nodes in heavy-fermion CeCoIn5 and the organic superconductor BEDT-TTF 2Cu NCS 2.