# Anomalous mesoscopic kinetics in disordered superconductors

## TL;DR

This paper investigates how mesoscopic fluctuations near the superconducting transition in disordered thin films lead to enhanced and non-universal transport phenomena, including large Nernst signals and thermoelectric effects.

## Contribution

It reveals the divergence of mesoscopic fluctuations near the transition and their strong dependence on dimensionality, temperature, and magnetic field, highlighting novel universal behaviors.

## Key findings

- Mesoscopic conductivity fluctuations become non-universal and can exceed normal state values.
- Superconducting correlations induce enhanced mesoscopic fluctuations in thermodynamic and transport properties.
- Unified temperature dependence observed across magnetic susceptibility, conductivity, and thermopower.

## Abstract

We study anomalous mesoscopic transport effects at the onset of the superconducting transition focusing on the observed large Nernst-Ettinghausen signal in disordered thin films. In the vicinity of the transition, as the Ginzburg-Landau coherence length of preformed Cooper pairs diverges, short-range mesoscopic fluctuations are equivalent to local fluctuations of the critical temperature. As a result, the dynamical susceptibility function of pair propagation acquires a singular mesoscopic component, and consequently, superconducting correlations give rise to enhanced mesoscopic fluctuations of thermodynamic and transport characteristics. In contrast to disordered normal metals, the root-mean-square value of mesoscopic conductivity fluctuations ceases to be universal and displays strong dependence on dimensionality, temperature, and under certain conditions can exceed its quantum normal state value by a large factor. Interestingly, we find different universality as magnetic susceptibility, conductivity, and transverse magnetic thermopower coefficients all display the same temperature dependence. Finally, we discuss an enhancement of mesoscopic effects in the Seebeck thermoelectricity and Hall conductivity fluctuations as mediated by emergent superconductivity.