Topological Edge Conduction Induced by Strong Anisotropic Exchange Interactions

TL;DR

This paper predicts that strong anisotropic exchange interactions in honeycomb materials can induce topological edge conduction with quantized Hall conductance, even without external magnetic fields, due to symmetry-breaking magnetic order.

Contribution

It introduces a mechanism where anisotropic exchange interactions induce topological edge states and quantized conductance in honeycomb lattice materials.

Findings

Topological edge conduction occurs when anisotropic exchange is at least twice the isotropic exchange.

Materials like Na$_2$IrO$_3$ can exhibit quantized Hall conductance without magnetic fields.

Strong anisotropic exchange induces magnetic order that breaks time-reversal symmetry.

Abstract

We predict that an interplay between isotropic and anisotropic exchange interactions in a honeycomb lattice structure can lead to topological edge conduction when the anisotropic interaction is at least twice the strength of the isotropic interaction. For materials like Na$_2$IrO$_3$, such a strong anisotropic exchange interaction simultaneously induces a zigzag type of antiferromagnetic order that breaks the time-reversal symmetry of the topological edge conductor. We show that the electronic transport in such topological conductors will exhibit a quantized Hall conductance without any external magnetic field when the Fermi energy lies within a particular energy range.