Finite-momentum mixed singlet-triplet pairing in chiral antiferromagnets induced by even-parity spin texture

TL;DR

This paper reveals a novel finite-momentum mixed singlet-triplet pairing in chiral antiferromagnets with unique spin textures, enabling tunable superconducting phases without net magnetization or spin-orbit coupling.

Contribution

It uncovers an exotic coexistence of singlet and triplet pairings induced by even-parity spin textures in chiral antiferromagnets, independent of spin-orbit coupling or net magnetization.

Findings

Finite-momentum mixed pairing states are induced in antiferromagnets.

A tunable phase difference between singlet and triplet pairs is demonstrated.

Predictions include observable Josephson effects like 0-$\\pi$ transitions.

Abstract

Non-relativistic spin-splitting in unconventional antiferromagnets has garnered much attention for its promising spintronic applications and open fundamental questions. Here, we uncover a unique even-parity spin texture in chiral non-collinear antiferromagnets, exemplified using a kagome lattice. We consider two distinct types of electrons in the system: one with Schr\"odinger-like dispersion and the other exhibiting Dirac-like behavior. Remarkably, we show that, for both electron types, this spin texture induces an exotic coexistence of opposite-spin singlet and equal-spin triplet Cooper pairs with finite momentum when proximity-coupled to conventional superconductors. The triplet pairing arises from the intrinsic spin rotation of the antiferromagnet and does not require net magnetization or spin-orbit coupling. Moreover, we identify an unprecedented and tunable phase difference between singlet and triplet pairings, controllable through junction orientation. This mixed pairing state can be experimentally probed via damped oscillations in order parameters and 0-$\pi$ transitions in Josephson junctions. Additionally, we analyze the effect of out-of-plane spin canting, elucidating its role in generating spin-polarized supercurrents, and discuss Mn$_3$Ga and Mn$_3$Ge to test our predictions.