Coherent Propagation of Spin Helices in a Quantum-Well Confined Electron Gas

TL;DR

This paper demonstrates the coherent propagation of spin helices in a high mobility quantum well, showing a transition from overdamped to coherent modes and achieving high spin polarization velocities under applied electric fields.

Contribution

It provides experimental evidence of coherent spin helix propagation in a quantum well and measures the associated velocities under electric fields, advancing spintronics understanding.

Findings

Transition from overdamped to coherent spin modes observed.

Spin polarization reaches velocities of 10^7 cm/s.

Coherent propagation persists over multiple spin-precession periods.

Abstract

We use phase-resolved transient grating spectroscopy to measure the propagation of spin helices in a high mobility $n$-GaAs/AlGaAs quantum well with an applied in-plane electric field. At relatively low fields helical modes crossover from overdamped excitations where the spin-precession period exceeds the spin lifetime, to a regime of coherent propagation where several spin-precession periods can be observed. We demonstrate that the envelope of a spin polarization packet reaches a current-driven velocity of 10$^7$ cm s$^{-1}$ in an applied field of 70 V cm$^{-1}$.