Oscillatory Dyakonov-Perel spin dynamics in two-dimensional electron gases

Leyland, W.J.H., Harley, R.T., Henini, M., Shields, A.J., Farrer, I. and Ritchie, D.A. (2007) Oscillatory Dyakonov-Perel spin dynamics in two-dimensional electron gases. Physical Review B, 76 (19), [195305]. (doi:10.1103/PhysRevB.76.195305).

Abstract

Optical pump-probe measurements of spin dynamics at temperatures down to 1.5 K are described for a series of (001)-oriented GaAs/AlGaAs quantum well samples containing high mobility two-dimensional electron gases (2DEGs). For well widths ranging from 5 to 20 nm and 2DEG sheet densities from 1.75×10¹¹ to 3.5×10¹¹ cm^-2, the evolution of a small injected spin population is found to be a damped oscillation rather than an exponential relaxation, consistent with the quasi-collision-free regime of the Dyakonov-Perel spin dynamics. A Monte Carlo simulation method is used to extract the spin-orbit-induced electron spin precession frequency |Ω(k_F)| and electron momentum scattering time τ_p* at the Fermi wave vector. The spin decay time passes through a minimum at a temperature corresponding to the transition from collision-free to collision-dominated regimes and τ_p* is found to be close to the ensemble momentum scattering time tp obtained from Hall measurements of electron mobility. The values of |Ω(k_F)| give the Dresselhaus or bulk inversion asymmetry (BIA) coefficient of spin-orbit interaction as a function of electron confinement energy in the quantum wells and show, qualitatively, the behavior expected from k·p theory.

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