Overflow of a dipolar exciton trap at high magnetic fields

TL;DR

This study investigates how high magnetic fields affect dipolar exciton traps in GaAs quantum wells, revealing a trap overflow phenomenon at high fields due to many-body interaction effects, with implications for exciton control.

Contribution

It provides new insights into exciton behavior at high magnetic fields, especially the trap overflow mechanism driven by Landau level occupation and interaction renormalization.

Findings

Exciton density roughly doubles up to 7 Tesla.

Trap overflow occurs independently of electrostatic potential depth.

Magnetic field influences exciton energetics via many-body interactions.

Abstract

We study laterally trapped dipolar exciton ensembles in coupled GaAs quantum wells at high magnetic fields in the Faraday configuration. In photoluminescence experiments, we identify three magnetic field regimes. At low fields, the exciton density is increased by a reduced charge carrier escape from the trap, and additionally, the excitons' emission energy is corrected by a positive diamagnetic shift. At intermediate fields, magnetic field dependent correction terms apply which follow the characteristics of a neutral magnetoexciton. Due to a combined effect of an increasing binding energy and lifetime, the exciton density is roughly doubled from zero to about seven Tesla. At the latter high field value, the charge carriers occupy only the lowest Landau level. In this situation, the exciton trap can overflow independently from the electrostatic depth of the trapping potential, and the energy shift of the excitons caused by the so-called quantum confined Stark effect is effectively compensated. Instead, the exciton energetics seem to be driven by the magnetic field dependent renormalization of the many-body interaction terms. In this regime, the impact of parasitic in-plane fields at the edge of trapping potential is eliminated.