Coherent transport and manipulation of spins in indirect exciton nanostructures

TL;DR

This paper demonstrates the coherent control and long-distance transport of spin states in indirect excitons within GaAs double quantum well nanostructures, highlighting their potential for quantum information applications.

Contribution

It provides the first detailed analysis of spin precession and transport in IXs, including direct measurement of spin splitting coefficients and insights into spin dynamics independence from IX density.

Findings

Spins precess while diffusing over 20 μm distances.

Spin precession frequency depends on transport direction and bias.

Long spin lifetimes are due to electron-hole separation, not collective effects.

Abstract

We report on the coherent control and transport of indirect exciton (IX) spins in GaAs double quantum well (DQW) nanostructures. The spin dynamics was investigated by optically generating spins using a focused, circularly polarized light spot and by probing their spatial distribution using spatially and polarization resolved photoluminescence spectroscopy. Optically injected exciton spins precess while diffusing over distances exceeding 20 {\mu}m from the excitation spot with a spatial precession frequency that depends on the spin transport direction as well as on the bias applied across the DQW structure. This behavior is attributed to the spin precession in the effective magnetic field induced by the spin-orbit interaction. From the dependence of the spin dynamics on the transport direction, bias and external magnetic fields we directly determined the Dresselhaus and Rashba spin splitting coefficients for the structure. The precession dynamics is essentially independent on the IX density, thus indicating that the long spin lifetimes are not associated with IX collective effects. The latter, together with the negligible contribution of holes to the spin dynamics, are rather attributed to spatial separation of the electron and hole wave functions by the electric field, which reduces the electron-hole exchange interaction. Coherent spin precession over long transport distances as well as the control of the spin vector using electric and magnetic fields open the way for the application of IX spins in the quantum information processing.