# Anti-chiral edge states in Heisenberg ferromagnet on a honeycomb lattice

## TL;DR

This paper reports the theoretical prediction of anti-chiral edge states in a Heisenberg ferromagnet on a honeycomb lattice with Dzyaloshinskii-Moriya interaction, revealing new magnon transport phenomena due to broken chiral symmetry.

## Contribution

It introduces the concept of anti-chiral edge states arising from asymmetric DMI in a ferromagnetic honeycomb lattice, a novel phenomenon not previously documented.

## Key findings

- Anti-chiral edge states can emerge with strong DMI asymmetry.
- Magnon currents propagate in the same direction along both edges.
- Broken chiral symmetry enables counter-propagating bulk currents.

## Abstract

We demonstrate the emergence of anti-chiral edge states in a Heisenberg ferromagnet with Dzyaloshinskii-Moriya interaction(DMI) on a honeycomb lattice with in-equivalent sub-lattices. The DMI, which acts between atoms of the same species, differs in magnitude for the two sub-lattices, resulting in a shifting of the energy of the magnon bands in opposite directions at the two Dirac points. The chiral symmetry is broken and for sufficiently strong asymmetry, the band shifting leads to anti-chiral edge states (in addition to the normal chiral edge states) in a rectangular strip where the magnon current propagates in the same direction along the two edges. This is compensated by a counter-propagating bulk current that is enabled by the broken chiral symmetry. We analyze the resulting magnon current profile across the width of the system in details and suggest realistic experimental probes to detect them. Finally, we propose a material that can potentially exhibit such anti-chiral edge states.