Edge excitons in a 2D topological insulator in the magnetic field

TL;DR

This paper investigates the properties of edge excitons in a 2D topological insulator under an in-plane magnetic field, revealing unique excitonic states and absorption characteristics influenced by the magnetic field.

Contribution

It introduces the concept of edge excitons in a 2D topological insulator with a magnetic field and analyzes their binding energies and optical transitions.

Findings

Edge excitons exist due to a narrow gap in electron edge states caused by the magnetic field.

Exciton binding energy is significantly smaller than typical 1D Coulomb energies.

Phototransitions occur on even exciton states, while odd states are optically dark.

Abstract

Exciton edge states and the microwave edge exciton absorption of a 2D topological insulator subject to the in-plane magnetic field are studied. The magnetic field forms a narrow gap in electron edge states that allows the existence of edge exciton. The exciton binding energy is found to be much smaller than the energy of a 1D Coulomb state. Phototransitions exist on the exciton states with even numbers, while odd exciton states are dark.