Spin dephasing and photoinduced spin diffusion in high-mobility 110-grown GaAs-AlGaAs two-dimensional electron systems

TL;DR

This study investigates spin dephasing and diffusion in high-mobility GaAs/AlGaAs quantum wells grown in the [110] direction, revealing long spin lifetimes at low excitation and the effects of optical excitation on spin dynamics.

Contribution

It provides new insights into spin lifetime behavior and diffusion distances in high-mobility 2D electron systems under varying optical excitation conditions.

Findings

Spin lifetimes exceed 16 ns at low excitation density.

Spin diffusion extends over more than 20 microns.

Higher pump intensity can increase spin polarization away from the pump spot.

Abstract

We have studied spin dephasing and spin diffusion in a high-mobility two-dimensional electron system, embedded in a GaAs/AlGaAs quantum well grown in the [110] direction, by a two-beam Hanle experiment. For very low excitation density, we observe spin lifetimes of more than 16 ns, which rapidly decrease as the pump intensity is increased. Two mechanisms contribute to this decrease: the optical excitation produces holes, which lead to a decay of electron spin via the Bir-Aranov-Pikus mechanism and recombination with spin-polarized electrons. By scanning the distance between the pump and probe beams, we observe the diffusion of spin-polarized electrons over more than 20 microns. For high pump intensity, the spin polarization in a distance of several microns from the pump beam is larger than at the pump spot, due to the reduced influence of photogenerated holes.