Crafting zero-bias one-way transport of charge and spin

TL;DR

This paper demonstrates how a metal on a 2D topological insulator can enable nearly perfect directional charge and spin transport, even at zero bias, through unique bandstructure engineering and selective edge state control.

Contribution

It introduces a novel approach to achieve zero-bias, one-way charge and spin transport by manipulating edge states in topological insulator-based heterostructures.

Findings

Selective switching off of edge states enables directional transport.

Coexistence of topological states with bulk states in the same system.

Potential application in van der Waals heterostructures and ultrathin topological insulators.

Abstract

We explore the electronic structure and transport properties of a metal on top of a (weakly coupled) two-dimensional topological insulator. Unlike the widely studied junctions between topological non-trivial materials, the systems studied here allow for a unique bandstructure and transport steering. First, states on the topological insulator layer may coexist with the gapless bulk and, second, the edge states on one edge can be selectively switched-off, thereby leading to nearly perfect directional transport of charge and spin even in the zero bias limit. We illustrate these phenomena for Bernal stacked bilayer graphene with Haldane or intrinsic spin-orbit terms and a perpendicular bias voltage. This opens a path for realizing directed transport in materials such as van der Waals heterostructures, monolayer and ultrathin topological insulators.