Quantum Geometry of Altermagnetic Magnons Probed by Light

TL;DR

This paper proposes using bicircular light as an optical probe to detect chiral altermagnetic magnons and their quantum geometry, providing a universal method to distinguish altermagnets from antiferromagnets through light-magnon interactions.

Contribution

It introduces bicircular Raman response as a novel optical technique to identify altermagnetic magnons and their quantum geometry, independent of magnon topology.

Findings

Bicircular light selectively probes magnon quantum geometry.

Enhanced nonlinear second-order light-magnon interactions in $d$-wave altermagnets.

Proposed universal protocol to distinguish altermagnets from antiferromagnets.

Abstract

Magnons with momentum-dependent chirality are a key signature of altermagnets. We identify bicircular light as a smoking-gun optical probe for chiral altermagnetic magnons, selectively targeting their quantum geometry induced by an alteration of magnonic chirality. We show that in $d$-wave altermagnets, under a canting magnetic field, the altermagnetic magnons realize a nontrivial quantum geometry, resulting in an enhancement of the nonlinear second-order light-magnon interactions. We find that the scattering of bicircular pulses probes the present magnon quantum geometry, even if the magnonic topology is trivial. Hence, our findings establish bicircular Raman response as an optical effect of choice to identify altermagnetic magnons. As such, we propose a universal experimental protocol to distinguish altermagnets from antiferromagnets by detecting their magnon chirality patterns with light, independently of the underlying magnon topology.