A Route to Nonrelativistic Altermagnetic Spin Splitting via Ultrafast Light

TL;DR

This paper proposes a novel nonequilibrium method using ultrafast light to induce altermagnetic spin splitting in antiferromagnets without relying on relativistic effects or external fields.

Contribution

It introduces a new ultrafast light-driven mechanism for generating altermagnetic spin splitting in antiferromagnets, demonstrated via real-time density functional theory.

Findings

Linearly polarized light induces momentum-dependent spin splitting.

The mechanism involves breaking effective time-reversal symmetry.

It extends altermagnetism into the nonequilibrium regime.

Abstract

We identify a nonequilibrium route for generating altermagnetic spin splitting in antiferromagnet by ultrafast light. Unlike existing strategies, this route does not require relativistic angular-momentum transfer, static symmetry breaking, or auxiliary external fields. Using real-time time-dependent density functional theory, we demonstrate in the antiferromagnetic perovskite KNiF3 that linearly polarized light can induce momentum-dependent altermagnetic spin splitting by breaking the effective time-reversal symmetry through photoexcited charge redistribution and the resulting lattice distortion. We provide a general symmetry selection rule for this route. These results establish a mechanism for ultrafast control of altermagnetism and extend its material realization into the nonequilibrium regime.