Enhancement of Superconductivity in Disordered Films by Parallel Magnetic Field

TL;DR

This paper demonstrates that applying a parallel magnetic field can enhance the superconducting transition temperature in highly disordered thin films by polarizing magnetic impurities, and predicts a novel magnetic-field-induced superconductivity phenomenon.

Contribution

It reveals how parallel magnetic fields can increase T_c in disordered films by reducing exchange scattering through impurity spin polarization, introducing a new way to control superconductivity.

Findings

T_c(H) can be increased by parallel magnetic field in disordered films.

Magnetic field can induce superconductivity in certain impurity concentration ranges.

Superconductivity persists in a nonzero field range due to impurity spin polarization.

Abstract

We show that the superconducting transition temperature T_c(H) of a very thin highly disordered film with strong spin-orbital scattering can be increased by parallel magnetic field H. This effect is due to polarization of magnetic impurity spins which reduces the full exchange scattering rate of electrons; the largest effect is predicted for spin-1/2 impurities. Moreover, for some range of magnetic impurity concentrations the phenomenon of {\it superconductivity induced by magnetic field} is predicted: superconducting transition temperature T_c(H) is found to be nonzero in the range of magnetic fields $0 < H^* <= H <= H_c$.