Electric-Field Tuning of Spin-Dependent Exciton-Exciton Interactions in Coupled Quantum Wells

TL;DR

This study demonstrates how an electric field can tune spin-dependent exciton interactions in coupled quantum wells, revealing the importance of wavefunction deformation and screening effects on exciton energy splitting.

Contribution

It provides experimental evidence of electric-field control over exciton spin interactions and introduces a new theoretical perspective on screening effects related to excitation power.

Findings

Electric field reduces exciton energy splitting from 4 meV to zero.

Wavefunction deformation explains the decrease in energy separation.

Screening modification is necessary to fully understand power dependence.

Abstract

We have shown experimentally that an electric field decreases the energy separation between the two components of a dense spin-polarized exciton gas in a coupled double quantum well, from a maximum splitting of $\sim 4$ meV to zero, at a field of $\sim $35 kV/cm. This decrease, due to the field-induced deformation of the exciton wavefunction, is explained by an existing calculation of the change in the spin-dependent exciton-exciton interaction with the electron-hole separation. However, a new theory that considers the modification of screening with that separation is needed to account for the observed dependence on excitation power of the individual energies of the two exciton components.