Magneto-optics of two-dimensional electron gases modified by strong Coulomb interactions in ZnSe quantum wells

TL;DR

This study investigates how strong Coulomb interactions modify the magneto-optical properties of two-dimensional electron gases in ZnSe quantum wells, revealing a transition from Landau-level-like to exciton-like spectra in high magnetic fields.

Contribution

It provides a phenomenological model describing the evolution of optical spectra in quantum wells with strong Coulomb interactions under magnetic fields.

Findings

Optical spectra are strongly influenced by Coulomb interactions.

Transition from Landau-level-like to exciton-like spectra occurs at high magnetic fields.

Fermi energy lies between trion and exciton binding energies.

Abstract

The optical properties of two-dimensional electron gases in ZnSe/(Zn,Be)Se and ZnSe/(Zn,Be,Mg)Se modulation-doped quantum wells with electron densities up to 1.4x10^{12} cm^{-2} were studied by photoluminescence, photoluminescence excitation and reflectivity in a temperature range between 1.6 and 70 K and in external magnetic fields up to 48 T. In these structures, the Fermi energy of the two-dimensional electron gas falls in the range between the trion binding energy and the exciton binding energy. Optical spectra in this regime are shown to be strongly influenced by the Coulomb interaction between electrons and photoexcited holes. In high magnetic fields, when the filling factor of the two-dimensional electron gas becomes smaller than two, a change from Landau-level-like spectra to exciton-like spectra occurs. We attempt to provide a phenomenological description of the evolution of optical spectra for quantum wells with strong Coulomb interactions.