Reentrant Superconductivity in Zeeman Fields

TL;DR

This paper presents a theoretical model demonstrating reentrant superconductivity in Zeeman fields, influenced by spin-orbit interactions and characterized by odd- and even-frequency Cooper pairs.

Contribution

It introduces a model where spin-orbit coupling modulates superconductivity under Zeeman fields, revealing conditions for reentrant behavior and pairing symmetry changes.

Findings

Superconductivity is suppressed in weak Zeeman fields and enhanced in strong fields due to spin-orbit interactions.

The stability of the superconducting state correlates with the emergence of odd-frequency Cooper pairs.

The model predicts reentrant superconductivity driven by the interplay of spin vectors and Zeeman effects.

Abstract

We propose a theoretical model for a superconductor that exhibits the reentrant superconductivity in Zeeman fields. The Bogoliubov-de Gennes Hamiltonian includes three vectors in spin space: a $d$ vector of a spin-triplet superconducting state, a potential representing spin-orbit interactions, and a Zeeman field. When the three vectors are perpendicular to one another, the spin-orbit interaction suppresses superconductivity in weak Zeeman fields and enhances superconductivity in strong Zeeman fields. The instability (stability) of superconducting state is characterized by the appearance of odd-frequency (even-frequency) Cooper pairs.