Spin-orbital coupling in a triplet superconductor-ferromagnet junction

TL;DR

This paper investigates the interaction between spin and orbital degrees of freedom at triplet superconductor-ferromagnet interfaces, revealing how magnetization orientation affects the superconducting gap and induces a first-order transition in chiral superconductors.

Contribution

It introduces a self-consistent mean-field theory to analyze orbitally-dependent spin-orbital coupling effects at superconductor-ferromagnet interfaces, highlighting the influence of gap symmetry on magnetization orientation.

Findings

Increasing the angle between ferromagnetic moment and triplet vector modulates the p-wave gap.

The preferred magnetization orientation depends on the orbital structure of the superconducting gap.

A first-order transition occurs between different magnetization states in chiral superconductors.

Abstract

We study a novel type of coupling between spin and orbital degrees of freedom which appears at triplet superconductor-ferromagnet interfaces. Using a self-consistent spatially-dependent mean-field theory, we show that increasing the angle between the ferromagnetic moment and the triplet vector order parameter enhances or suppresses the p-wave gap close to the interface, according as the gap antinodes are parallel or perpendicular to the boundary, respectively. The associated change in condensation energy establishes an orbitally-dependent preferred orientation for the magnetization. When both gap components are present, as in a chiral superconductor, we observe a first-order transition between different moment orientations as a function of the exchange field strength.