Manifestation of axion electrodynamics through magnetic ordering on edges of topological insulator

TL;DR

This paper demonstrates that work function differences on topological insulator surfaces induce magnetic ordering along edges, illustrating axion electrodynamics effects in real materials.

Contribution

It reveals how work function disparities lead to magnetic edge states in topological insulators, connecting surface chemistry with axion electrodynamics phenomena.

Findings

Work function differences cause magnetic ordering at edges.

Magnetic ordering depends on facet work function disparity.

The phenomenon exemplifies axion electrodynamics in solids.

Abstract

Based on a first-principles approach, we show that in a single crystal of a prototypical topological insulator such as Bi$_2$Se$_3$ the difference in the work function between adjacent surfaces with different crystal-face orientations generates a built-in electric field around facet edges. Owing to the topological magnetoelectric coupling for a given broken time-reversal symmetry in the crystal, the electric field, in turn, forces effective magnetic dipoles to accumulate along the edges, realizing the facet-edge magnetic ordering. We demonstrate that the predicted magnetic ordering which depends only on the work function difference between facets, is in fact a manifestation of the axion electrodynamics in real solids.