Thermal conductivity in a mixed state of a superconductor at low magnetic fields

Abstract

We evaluate accurate low-field/low-temperature asymptotics of the thermal conductivity perpendicular to magnetic field for one-band and two-band s-wave superconductors using Keldysh-Usadel formalism. We show that heat transport in this regime is limited by tunneling of quasiparticles between adjacent vortices across a number of local points and therefore widely-used approximation of averaging over circular unit cell is not valid. In the single-band case, we obtain parameter-free analytical solution which provides theoretical lower limit for heat transport in the mixed state. In the two-band case, we show that heat transport is controlled by the ratio of gaps and diffusion constants in different bands. Presence of a weaker second band strongly enhances the thermal conductivity at low fields

7 pages, 1 figure, discussion of the clean case and discussion of experiment added

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• Negative thermal magnetoresistivity as a signature of chiral anomaly in Weyl superconductors
• Superconducting gap structure of the skutterudite LaPt4Ge12 probed by specific heat and thermal transport
• Direct visualization of quasiparticle concentration around superconducting vortices
• Anisotropy of the superconducting fluctuations in multiband superconductors: the case of LiFeAs
• Thermal properties of the superconductor-quantum Hall interfaces