Universal Thermal and Electrical Transport Near the Superconductor-Metal Quantum Phase Transition in Nanowires

Abstract

We describe the thermal ((\kappa)) and electrical ((\sigma)) conductivities of quasi-one-dimensional wires, across a quantum phase transition from a superconductor to a metal induced by pair-breaking perturbations. Fluctuation corrections to BCS theory motivate a field theory for quantum criticality. We describe deviations in the Wiedemann-Franz ratio (\kappa∕\sigma T) (where (T) is the temperature) from the Lorenz number ((\pi^2∕3)(k_B∕e)^2), which can act as sensitive tests of the theory. We also describe the crossovers out of the quantum-critical region into the metallic and superconducting phases.