A novel superconducting glass state in disordered thin films in Clogston limit

TL;DR

This paper develops a theory describing a new superconducting glass state in disordered thin films under a parallel magnetic field, revealing a phase transition to a state with randomly signed superfluid densities and universal mesoscopic pairing statistics.

Contribution

It introduces a novel superconducting glass phase in disordered thin films at the Clogston limit, linking mesoscopic fluctuations to a 2D XY spin glass universality class.

Findings

Superconducting state transitions to a glassy phase with random superfluid signs.

Mesoscopic pairing states nucleate in a spin polarized Fermi liquid.

Universal pairing statistics depend on the film's sheet conductance.

Abstract

A theory of mesoscopic fluctuations in disordered thin superconducting films in a parallel magnetic field is developed. At zero temperature, the superconducting state undergoes a phase transition into a state characterized by superfluid densities of random signs, instead of a spin polarized disordered Fermi liquid phase. Consequently, the ground state belongs to the same universality class as the 2D XY spin glass. As the magnetic field increases further, mesoscopic pairing states are nucleated in an otherwise homogeneous spin polarized disordered Fermi liquid. The statistics of these pairing states is universal depending on the sheet conductance of the 2D film.