Signatures of enhanced spin-triplet superconductivity induced by interfacial properties

TL;DR

This paper investigates how interfacial properties like barrier strength and spin-orbit coupling influence the enhancement of spin-triplet superconductivity in junctions, revealing a nonmonotonic relationship and identifying conditions for maximum enhancement.

Contribution

It demonstrates that an optimal intermediate level of interfacial barrier and spin-orbit coupling maximizes spin-triplet superconductivity, supported by conductance signatures and self-consistent calculations.

Findings

Enhanced spin-triplet superconductivity occurs at intermediate interfacial barrier and spin-orbit coupling.

Large magnetoanisotropy of conductance correlates with enhanced spin-triplet pairing.

Predicted further enhancement of conductance magnetoanisotropy at finite bias.

Abstract

While spin-triplet pairing remains elusive in nature, there is a growing effort to realize proximity-induced equal-spin triplet superconductivity in junctions with magnetic regions or an applied magnetic field and common $s$-wave superconductors. To enhance such spin-triplet contribution, it is expected that junctions with a weak interfacial barrier and strong spin-orbit coupling are desirable. Intuitively, a weak interfacial barrier enables a robust proximity-induced superconductivity and strong spin-orbit coupling promotes spin mixing, converting spin-singlet into spin-triplet superconductivity. In contrast, we reveal a nonmonotonic spin-triplet contribution with the strength of the interfacial barrier and spin-orbit coupling. This picture is established by considering different signatures in conductance and superconducting correlations, as well as by performing self-consistent calculations. As a result, we identify a strongly enhanced spin-triplet superconductivity, realized for an intermediate strength of interfacial barrier and spin-orbit coupling. In junctions with magnetic regions, an enhanced spin-triplet superconductivity leads to a large magnetoanisotropy of conductance and superconducting correlations. This picture of an enhanced spin-triplet superconductivity is consistent with experiments demonstrating a huge increase in the conductance magnetoanisotropy, which we predict can be further enhanced at a finite bias.