Interfacial spin-orbit coupling driven enhancement of superconductivity by parallel magnetic field

TL;DR

This paper explains how interfacial spin-orbit coupling combined with a parallel magnetic field can enhance superconductivity and increase the critical temperature in thin films, challenging the conventional view of magnetic fields always suppressing superconductivity.

Contribution

It introduces a theoretical model showing that Rashba spin-orbit interaction and magnetic field can boost superconductivity, supported by calculations of critical temperature modifications.

Findings

Superconducting critical temperature can be enhanced by parallel magnetic field.

Interfacial spin-orbit interaction causes Lifshitz invariants affecting superconductivity.

Modification of Little-Parks oscillations due to Rashba spin-orbit coupling.

Abstract

It is commonly believed that time reversal symmetry breaking perturbations such as magnetic field or scattering on magnetic impurities destruct superconductivity and suppress the critical temperature of the superconducting phase transition. However, in the recent experimental studies significant enhancement of superconducting critical temperature by parallel magnetic field was found for several thin superconducting systems [H.J. Gardner, et al., Nature Physics {\bf 7}, 895 (2011); T. Asaba, et al., Scientific Reports {\bf 8}, 1 (2018) ]. Here we present a possible explanation of the observed phenomenon showing that combination of interfacial spin-orbit interaction and external magnetic field can cause the increase of the superconducting critical temperature of thin superconducting film in wide range of magnetic fields. We use the Ginzburg-Landau formalism taking into account Lifshitz invariant originated from Rashba spin-orbit interaction, which is also responsible for the superconducting diode effect. We also calculate the modification of the Little-Parks oscillations of the critical temperature of hollow superconducting cylinder at the presence of Rashba interfacial spin-orbit interaction.