Low-dissipation edge currents without edge states

TL;DR

This paper demonstrates that bulk carriers in trivial multi-valley insulators with Berry curvature can produce low-dissipation edge currents without the need for edge states, driven by inhomogeneous orbital magnetization near edges.

Contribution

It reveals a new mechanism for low-dissipation edge currents in topologically trivial insulators, independent of edge states or topological protection.

Findings

Edge currents are localized within the valley diffusion length from the edge.

These currents can mimic ballistic transport in clean devices.

The effect occurs even with thermally activated bulk carriers.

Abstract

We show that bulk free carriers in topologically trivial multi-valley insulators with non-vanishing Berry curvature give rise to low-dissipation edge currents, which are squeezed within a distance of the order of the valley diffusion length from the edge. This happens even in the absence of edge states [topological (gapless) or otherwise], and when the bulk equilibrium carrier concentration is thermally activated across the gap. Physically, the squeezed edge current arises from the spatially inhomogeneous orbital magnetization that develops from valley-density accumulation near the edge. While this current possesses neither topology nor symmetry protection and, as a result, is not immune to dissipation, in clean enough devices it can mimic low-loss ballistic transport.