Spin-Valley Locking and Pure Spin-Triplet Superconductivity in Noncollinear Antiferromagnets Proximitized to Conventional Superconductors

TL;DR

This paper reveals a new spin-valley locking mechanism in noncollinear antiferromagnets that enables pure spin-triplet superconductivity through proximity effects, independent of spin-orbit coupling or net magnetization, with robust supercurrents under magnetic fields.

Contribution

It uncovers a novel spin-valley locking phenomenon in noncollinear antiferromagnets and demonstrates the realization of pure spin-triplet superconductivity without relying on spin-orbit coupling.

Findings

Spin-triplet pairing is favored in chiral antiferromagnetic kagome lattices.

The spin-triplet supercurrent is resilient to Zeeman fields.

Spin-valley locking suppresses spin-singlet pairing away from interfaces.

Abstract

Unconventional antiferromagnets with spin-split bands, such as noncollinear magnets and the recently discovered altermagnets, serve as new constituents to explore unconventional superconductivity. Here, we unveil a new type and previously unappreciated nature of spin-valley locking in noncollinear antiferromagnets and exploit this texture to achieve pure spin-triplet superconductivity. Using chiral antiferromagnetic kagome lattices (e.g., Mn$_3$Ge and Mn$_3$Ga) coupled to conventional $s$-wave superconductors as prototypical examples, we demonstrate that the antiferromagnetic chirality strongly favors spin-triplet pairing via superconducting proximity effect, while suppressing spin-singlet pairing in the antiferromagnets away from the interfaces. Crucially, such a long-sought spin-triplet superconducting state is established without invoking the prevailing mechanism of spin-orbit coupling or net magnetization. Furthermore, the spin-triplet supercurrent is resilient to both in-plane and out-of-plane Zeeman fields, which exhibits distinct superiority to Ising superconductivity, serving as a compelling experimental signature of the triplet pairing and spin-valley-locked texture.