Long exciton spin memory in coupled quantum wells

TL;DR

This study demonstrates long-lasting exciton spin memory in coupled quantum wells, with polarization persisting well beyond exciton radiative lifetimes, indicating potential for spin-based quantum information applications.

Contribution

It provides direct experimental evidence of long exciton spin relaxation times in coupled quantum wells, surpassing previous lifetime measurements.

Findings

Achieved >50% circular polarization in emission.

Observed spin memory lasting tens of nanoseconds.

Spin relaxation time exceeds exciton radiative lifetime.

Abstract

Spatially indirect excitons in a coupled quantum well structure were studied by means of polarization and time resolved photoluminescence. A strong degree of circular polarization (> 50%) in emission was achieved when the excitation energy was tuned into resonance with the direct exciton state. The indirect transition remained polarized several tens of nanoseconds after the pumping laser pulse, demonstrating directly a very long relaxation time of exciton spin. The observed spin memory effect exceeds the radiative lifetime of the indirect excitons.