Novel Nonreciprocal Acoustic Effects in Antiferromagnets

TL;DR

This paper predicts novel nonreciprocal acoustic effects in antiferromagnets without external magnetic fields, based on microscopic and symmetry analyses, including boundary effects and directional phonon velocity differences.

Contribution

It introduces two new nonreciprocal effects in antiferromagnets, expanding understanding of magnetoelastic interactions without external magnetic influence.

Findings

Prediction of boundary-condition induced nonreciprocal effects

Existence of transversal phonon modes with different velocities in opposite directions

Suggestions of materials where these effects could be observed

Abstract

The possible occurrence of nonreciprocal acoustic effects in antiferromagnets in the absence of an external magnetic field is investigated using both (i) a microscopic formulation of the magnetoelastic interaction between spins and phonons and (ii) symmetry arguments. We predict for certain antiferromagnets the existence of two new nonreciprocal (non-time invariant) effects: A boundary-condition induced nonreciprocal effect and the occurrence of transversal phonon modes propagating in opposite directions having different velocities. Estimates are given and possible materials for these effects to be observed are suggested.