Deterministic Electrical Switching in Altermagnets via Surface Antisymmetry Groups

TL;DR

This paper introduces a surface antisymmetry group framework to determine how to achieve deterministic electrical switching of the Néel vector in altermagnets, focusing on surface effects and symmetry considerations.

Contribution

It develops a symmetry-based design rule framework for deterministic electrical switching in altermagnets using surface antisymmetry groups.

Findings

Surface antisymmetry groups determine interfacial effective fields.

Certain surface orientations enable transverse spin current generation.

Design rules are robust against surface roughness and facet averaging.

Abstract

A surface antisymmetry group framework is developed to establish design rules for deterministic electrical switching of the N\'eel vector in a film of a collinear bipartite antiferromagnet. In centrosymmetric $d$-wave altermagnets, where current-induced torques vanish in the bulk, staggered effective fields can nevertheless exist as an interfacial response, whose allowed tensor form is determined by the surface antisymmetry subgroup for the given surface orientation. Separately, the structure of the spin conductivity tensor determines which surface orientations allow transverse spin current generation via the spin-splitter effect. Taken together, these symmetry-enforced properties establish which surface orientations of $d$-wave altermagnets can serve as deterministically switchable spin current sources in spin-torque heterostructures. Because the design rules are based solely on the surface antisymmetry point group, the required staggered axial response is robust against averaging over symmetry-equivalent surface facets and equilibrium roughness.