Effects of scattering on the field-induced Tc enhancement in thin superconducting films in a parallel magnetic field

TL;DR

This paper revisits the effect of a parallel magnetic field on thin superconducting films using microscopic BCS theory, revealing how scattering influences Tc enhancement and phase transitions, including phenomena like re-entrant superconductivity.

Contribution

It provides a detailed microscopic analysis of scattering effects on Tc enhancement in thin films under magnetic fields, extending classical Ginzburg-Landau results to arbitrary temperatures.

Findings

Transport scattering shifts phase transition to higher fields and temperatures.

Tc enhancement diminishes in the dirty limit.

Re-entrant superconductivity can occur due to magnetic ions.

Abstract

The problem of a thin superconducting film in a parallel magnetic field, first discussed in the classical paper by Ginzburg and Landau for temperatures close to the critical, is revisited with the help of the microscopic BCS theory for arbitrary temperatures taking pair-breaking and transport scattering into account. While confirming experimental findings of the $T_c$ enhancement by the magnetic field, we find that the transport scattering pushes the phase transition curve to higher fields and higher temperatures for nearly all practical scattering rates. Still, the $T_c$ enhancement disappears in the dirty limit. We also consider intriguing changes, such as re-entrant superconductivity, caused to the phase boundary by pair-breaking magnetic ions spread on one of the film faces. These features await experimental verification.