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.
@article{arxiv.1512.04733,
title = {Edge excitons in a 2D topological insulator in the magnetic field},
author = {M. V. Entin L. I. Magarill and M. M. Mahmoodian},
journal= {arXiv preprint arXiv:1512.04733},
year = {2016}
}