Internal transitions of quasi-2D charged magneto-excitons in the presence of purposely introduced weak lateral potential energy variations

TL;DR

This study investigates how weak lateral potential energy variations affect internal transitions of charged magneto-excitons in quasi-2D GaAs/AlGaAs quantum wells, revealing bound-to-bound transitions due to symmetry breaking.

Contribution

It demonstrates the impact of intentionally introduced well-width variations on internal exciton transitions, highlighting the emergence of bound-to-bound transitions in magneto-excitons.

Findings

Bound-to-continuum transitions observed in samples without growth interrupts.

Bound-to-bound transitions appear in samples with well-width variations.

Symmetry breaking enables new excitonic transitions.

Abstract

Optically detected resonance spectroscopy has been used to investigate effects of weak random lateral potential energy fluctuations on internal transitions of charged magneto-excitons (trions) in quasi two-dimensional GaAs/AlGaAs quantum-well (QW) structures. Resonant changes in the ensemble photoluminescence induced by far-infrared radiation were studied as a function of magnetic field for samples having: 1) no growth interrupts (short range well-width fluctuations), and 2) intentional growth interrupts (long range monolayer well-width differences). Only bound-to-continuum internal transitions of the negatively charged trion are observed for samples of type 1. In contrast, a feature on the high field (low energy) side of electron cyclotron resonance is seen for samples of type 2 with well widths of 14.1 and 8.4 nm. This feature is attributed to a bound-to-bound transition of the spin-triplet with non-zero oscillator strength resulting from breaking of translational symmetry.