Giant Hyperfine Interaction between a Dark Exciton Condensate and Nuclei

TL;DR

This study demonstrates a significant hyperfine interaction enhancement between a dark exciton condensate and nuclei in GaAs/AlGaAs quantum wells, revealing nuclear polarization effects linked to the condensate's collective nature.

Contribution

It provides experimental evidence of nuclear polarization induced by a dark exciton condensate and shows a two-order magnitude increase in hyperfine interaction due to collective effects.

Findings

Nuclear polarization extends beyond excitation area and persists for seconds.

Hyperfine interaction is enhanced by two orders of magnitude.

The enhancement is attributed to the collective nature of the N-excitons condensate.

Abstract

We study the interaction of a dark exciton Bose-Einstein condensate with the nuclei in GaAs/AlGaAs coupled quantum wells and find clear evidence for nuclear polarization buildup that accompanies the appearance of the condensate. We show that the nuclei are polarized throughout the mesa area, extending to regions which are far away from the photoexcitation area, and persisting for seconds after the excitation is switched off. Photoluminescence measurements in the presence of RF radiation reveal that the hyperfine interaction between the nuclear and electron spins is enhanced by two orders of magnitude. We suggest that this large enhancement manifests the collective nature of the N-excitons condensate, which amplifies the interaction by a factor of sqrt{N}.