Edge absorption and pure spin current in 2D topological insulator in the Volkov-Pankratov model

TL;DR

This paper investigates how light absorption in 2D topological insulators induces pure spin currents along the edges, highlighting the role of in-plane electric fields and proposing a method for spin current measurement via luminescence.

Contribution

It introduces a model for edge absorption in 2D TIs and demonstrates the generation of pure spin photocurrents under specific electric field orientations.

Findings

Absorption occurs only for in-plane electric fields orthogonal to the edge.

Light absorption is accompanied by pure spin photocurrent along the edge.

Potential for measuring spin currents using polarized luminescence from quantum dots.

Abstract

The light absorption due to the transitions between the edge and two-dimensional (2D) states of a 2D topological insulator (TI) is considered in the Volkov-Pankratov model. It is shown that the transitions are allowed only for the in-plane electric field orthogonal to the edge of the TI. It is found that the absorption is accompanied by the pure spin photocurrent along the TI edge. The possibility of the spin current measurement using polarized luminescence from 2D TI quantum dots is discussed.