Charged magnetoexcitons in two dimensions: Magnetic translations and families of dark states

TL;DR

This paper reveals a new selection rule for optical transitions of charged excitons in magnetic fields, showing the spin-triplet ground state is optically inactive and identifying spectral features that distinguish localized from free excitons.

Contribution

It introduces a novel exact selection rule based on magnetic translations and characterizes the optical inactivity of the triplet ground state of charged excitons in magnetic fields.

Findings

Spin-triplet ground state of charged excitons is optically inactive.

Internal bound-to-bound triplet transition is below electron cyclotron resonance.

Spectral features can distinguish localized from free charged excitons.

Abstract

We show that optical transitions of charged excitons in semiconductor heterostructures are governed in magnetic fields by a novel exact selection rule, a manifestation of magnetic translations. It is shown that the spin-triplet ground state of the quasi-two-dimensional charged exciton X- --- a bound state of two electrons and one hole --- is optically inactive in photoluminescence at finite magnetic fields. Internal bound-to-bound X- triplet transition has a specific spectral position, below the electron cyclotron resonance, and is strictly prohibited in a translationally-invariant system. These results allow one to discriminate between localized and free charged excitons.