Fermi Surface Spin Texture and Topological Superconductivity in Spin-Orbit Free Non-Collinear Antiferromagnets

TL;DR

This paper investigates how non-collinear antiferromagnetic order in metals without spin-orbit coupling induces complex spin textures on the Fermi surface, which in turn influence the superconducting gap structure and enable topological superconductivity.

Contribution

It extends the concept of altermagnetism to non-collinear spin structures and shows how magnetic order can generate momentum-dependent spin textures affecting superconductivity.

Findings

Non-collinear magnetic order creates Fermi surface spin textures without spin-orbit coupling.

Spin textures constrain the superconducting gap structure, leading to nodal and topological features.

Example on kagome lattice demonstrates emergence of odd-parity topological superconductivity.

Abstract

We explore the relationship among the magnetic ordering in real space, the resulting spin texture on the Fermi surface, and the related superconducting gap structure in non-collinear antiferromagnetic metals without spin-orbit coupling. Via a perturbative approach, we show that a non-collinear magnetic ordering in a metal can generate a momentum-dependent spin texture on its Fermi surface, even in the absence of spin-orbit coupling, if the metal has more than three sublattices in its magnetic unit cell. Thus, our theory naturally extends the idea of altermagnetism to non-collinear spin structures. When superconductivity is developed in a magnetic metal, as the gap-opening condition is strongly constrained by the spin texture, the nodal structure of the superconducting state is also enforced by the magnetism-induced spin texture. Taking the non-collinear antiferromagnet on the kagome lattice as a representative example, we demonstrate how the Fermi surface spin texture induced by noncollinear antiferromagnetism naturally leads to odd-parity spin-triplet superconductivity with nontrivial topological properties.