Microscopic theory of in-plane critical field in two-dimensional Ising superconducting systems

TL;DR

This paper develops a microscopic theory explaining how in-plane critical magnetic fields in 2D Ising superconductors exceed the Pauli limit, influenced by spin-orbit interactions and impurities, aligning with recent experimental findings.

Contribution

It introduces a comprehensive microscopic framework accounting for spin-orbit effects and impurities in 2D Ising superconductors, explaining their high critical fields.

Findings

Critical fields surpass the Pauli limit due to spin polarization.

Impurity scattering and Rashba coupling weaken the critical field differently.

Theory matches experimental data in stanene and Pb thin films.

Abstract

We study the in-plane critical magnetic field of two-dimensional Ising superconducting systems, and propose the microscopic theory for these systems with or without inversion symmetry. Protected by certain specific spin-orbit interaction which polarizes the electron spin to the out-of-plane direction, the in-plane critical fields largely surpass the Pauli limit and show remarkable upturn in the zero temperature limit. The impurity scattering and Rashba spin-orbit coupling, treated on equal-footing in the microscopic framework, both weaken the critical field but in qualitatively different manners. The microscopic theory is consistent with recent experimental results in stanene and Pb superconducting ultra-thin films.