Nonreciprocal spin waves in a chiral antiferromagnet without the Dzyaloshinskii-Moriya interaction

TL;DR

This paper demonstrates that non-reciprocal spin waves can occur in a chiral antiferromagnet without relying on the Dzyaloshinskii-Moriya interaction, expanding understanding of spin wave behavior in magnetic materials.

Contribution

It reveals that non-reciprocal spin waves can arise solely from symmetric exchange interactions and external magnetic fields, without the need for DMI in chiral antiferromagnets.

Findings

Non-reciprocal spin waves observed without DMI.

Asymmetric energy gap shift under magnetic field.

Non-reciprocity driven by exchange interactions and external field.

Abstract

Non-reciprocal spin wave can facilitate the realization of spin wave logic devices. It has been demonstrated that the non-reciprocity can emerge when an external magnetic field is applied to chiral magnets, of which spin structures depend crucially on an asymmetric exchange interaction, that is, the Dzyaloshinskii-Moriya interaction (DMI). Here we demonstrate that the non-reciprocity can arise even without the DMI. We demonstrate this idea for the chiral antiferromagnet Ba$_2$NbFe$_3$Si$_2$O$_{14}$, of which DMI is very small and chiral spin structure arises mainly from the competition between symmetric exchange interactions. We show that when an external magnetic field is applied, asymmetric energy gap shift occurs and the spin wave becomes non-reciprocal from the competition between symmetric exchange interactions and the external magnetic field.