Quantum-fluctuation effects in transport properties of superconductors above the paramagnetic limit

TL;DR

This paper investigates how quantum fluctuations influence transport in ultrathin disordered superconducting films near the quantum critical point, revealing negative magnetoresistance effects at zero temperature.

Contribution

It provides a detailed calculation of quantum fluctuation corrections to conductivity, highlighting the equal importance of different fluctuation contributions at zero temperature.

Findings

Quantum fluctuations cause negative magnetoresistance.

All fluctuation contributions are of the same order at zero temperature.

Results agree qualitatively with recent experiments on disordered films and oxide interfaces.

Abstract

We study the transport in ultrathin disordered film near the quantum critical point induced by the Zeeman field. We calculate corrections to the normal state conductivity due to quantum pairing fluctuations. The fluctuation-induced transport is mediated by virtual rather than real quasi-particles. We find that at zero temperature, where the corrections come from purely quantum fluctuations, the Aslamazov-Larkin paraconductivity term, the Maki-Thompson interference contribution and the density of states effects are all of the same order. The total correction leads to the negative magnetoresistance. This result is in qualitative agreement with the recent transport observations in the parallel magnetic field of the homogeneously disordered amorphous films and superconducting two-dimensional electron gas realized at the oxide interfaces.