Fine structure of the exciton absorption in semiconductor superlattices in crossed electric and magnetic fields

TL;DR

This paper analytically investigates the fine structure of exciton absorption in semiconductor superlattices under crossed electric and magnetic fields, revealing how external fields and exciton motion influence spectral features.

Contribution

It provides an analytical framework for understanding exciton absorption spectra in superlattices with external fields, highlighting the effects of field orientation and exciton momentum.

Findings

Spectral fine structure is related to exciton states near Landau energies.

Field orientation and exciton momentum significantly affect absorption peaks.

Conditions for experimental observation are discussed.

Abstract

The exciton absorption coefficient is determined analytically for a semiconductor superlattice in crossed electric and magnetic fields, for the magnetic field being parallel and the electric field being perpendicular to the superlattice axis. Our investigation applies to the case where the magnetic length, while being much smaller than the exiton Bohr radius, considerably exceeds the superlattice period. The optical absorption in superlattices displays a spectral fine structure related to the sequences of exciton states bound whose energies are adjacent to the Landau energies of the charge carriers in the magnetic field. We study effects of external fields and of the centre-of-mass exciton motion on the fine structure peak positions and oscillator strengths. In particular, we find that the inversion of the orientation of the external fields and of the in-plane total exciton momentum notably affects the absorption spectrum. Conditions for the experimental observation of the exciton absorption are discussed.