Superconducting Fluctuation Corrections to the Thermal Current in Granular Metals

TL;DR

This paper calculates how superconducting fluctuations affect thermal conductivity in granular metals, revealing suppression near the critical temperature and violations of the Wiedemann-Franz law.

Contribution

It provides the first detailed calculation of fluctuation corrections to thermal conductivity in granular metals, highlighting temperature-dependent behaviors.

Findings

Thermal conductivity is suppressed near T_c proportional to T_c/(T-T_c).

Correction saturates close to T_c with sign depending on barrier transparency.

Wiedemann-Franz law is violated in both fluctuation regimes.

Abstract

The first-order superconducting fluctuation corrections to the thermal conductivity of a granular metal are calculated. A suppression of thermal conductivity proportional to $T_c/(T-T_c)$ is observed in a region not too close to the critical temperature $T_c$. As $T\simeq T_c$, a saturation of the correction is found, and its sign depends on the ratio between the barrier transparency and the critical temperature. In both regimes, the Wiedemann-Franz law is violated.