Direction-selective triplet pairing and spin-edge locking in altermagnetic metals

TL;DR

This paper explores how altermagnetic spin splitting influences unconventional superconductivity, leading to anisotropic triplet pairing and spin-resolved Majorana states in a 2D system.

Contribution

It reveals that intrinsic altermagnetic spin splitting can induce unconventional triplet pairing and spin-resolved Majorana boundary states without external magnetic fields.

Findings

Altermagnetic spin splitting suppresses singlet pairing.

Directional triplet pairing creates nearly dispersionless Majorana boundary states.

Rashba spin-orbit coupling induces mixed-parity superconductivity with dispersive Majorana states.

Abstract

We investigate self-consistent unconventional superconductivity in a two-dimensional $d$-wave altermagnetic metal. We find that momentum-dependent altermagnetic spin splitting suppresses opposite-spin singlet pairing and stabilizes highly anisotropic equal-spin triplet order. In the spin-conserving limit, this directional triplet pairing gives rise to nearly dispersionless Majorana boundary states associated with effective one-dimensional topological channels. Rashba spin-orbit coupling mixes spin sectors, activates additional pairing components, and drives the system into a mixed-parity superconducting state with dispersive Majorana boundary states. The spin-resolved boundary spectra further reveal a characteristic locking between boundary orientation and spin polarization, reflecting the underlying altermagnetic symmetry. These results identify altermagnetic spin splitting as an intrinsic mechanism for selecting unconventional pairing and generating spin-resolved Majorana boundary states without external magnetic fields.