Quantization of interface currents

TL;DR

This paper proves that interface currents between two 2D quantum systems are quantized by the difference in their Chern numbers, and discusses spin-polarized currents at interfaces of time-reversal invariant systems.

Contribution

It establishes a rigorous link between interface current quantization and topological invariants, extending quantum Hall concepts to interface phenomena.

Findings

Interface currents are macroscopically quantized by Chern number differences.

At certain interfaces, dissipationless spin-polarized currents can occur.

Quantitative relation between topological invariants and observable currents.

Abstract

At the interface of two two-dimensional quantum systems, there may exist interface currents similar to edge currents in quantum Hall systems. It is proved that these interface currents are macroscopically quantized by an integer that is given by the difference of the Chern numbers of the two systems. It is also argued that at the interface between two time-reversal invariant systems with half-integer spin, one of which is trivial and the other non-trivial, there are dissipationless spin-polarized interface currents.