Dynamical formation and active control of persistent spin helices in III-V and II-VI quantum wells

Abstract

This review article summarizes recent developments related to the dynamical formation of persistent spin helices in GaAs-and CdTe-based heterostructures. We start with fundamental aspects of spin-orbit interaction in quantum wells, in particular the Dresselhaus and Rashba terms and their relation to the bulk and structural inversion asymmetries, respectively. In the regime of balanced interactions, their combined impact gives rise to the formation of the persistent spin helix, i.e., a regime where a unidirectional spin grating with enhanced coherence time is established. The experimental scheme relies on ultrafast Kerr microscopy and permits to excite the spin polarization and detect it with a simultaneous spatial and temporal resolution of micrometers and picoseconds, respectively. For a microscopic understanding and a description of the results, kinetic theory of spatio-temporal spin dynamics of two-dimensional electrons is presented. In addition, Monte Carlo simulations of the spin distribution function are performed. Based on these concepts we discuss three areas with recent advances in the field of spin helices. (i) Anisotropic spin transport and spin helix dynamics in a modulation-doped GaAs quantum well is analyzed. It is observed that application of an out-of-plane electric field changes spinorbit interaction through the Rashba component and the cubic Dresselhaus term. Remarkably, a weak in-plane electric field substantially increases spin diffusion and also affects the spin helix wavelength. (ii) In-plane magnetic fields applied in two perpendicular orientations allow for the extraction of the individual spin-orbit coupling parameters. (iii) Finally, we explore the influence of optical doping on the spin helix in a CdTe quantum well. Most importantly, a non-uniform spatio-temporal precession pattern is observed. The kinetic theory of spin diffusion allows us to model this finding by incorporating a dependence on the photo-carrier density into the Rashba and the Dresselhaus parameters.

Theory of optically detected spin noise in nanosystems

“…Ref. [134], see also a review [135], where the experimental data concerning the observation of the spin helix in the spin diffusion are given. Spatio-temporal spin noise is characterized by the correlation function [cf.…”

Spin precession of light holes in the spin-orbit field of strained GaAs nanowires

“…The effect of spin-orbit interaction on the electronic spin in the conduction band has been investigated in detail because of potential applications using the spin degree of freedom for information transfer [1][2][3][4][5]. In particular, the electron spin has been shown to exhibit precessions over long distances with limited losses caused by spin relaxation (the persistent spin helix) [6][7][8][9][10].…”

Spin splitting in low-symmetry quantum wells beyond Rashba and Dresselhaus terms

“…Zero-field spin splitting of electron and hole subbands in semiconductors caused by spin-orbit (SO) interaction gives rise to a variety of exciting phenomena which are being explored for technological applications [1][2][3] . Examples are the intrinsic and intrinsic inverse spin Hall effects 4,5 , the spin-galvanic effect [6][7][8][9] and spin orientation by electric current 10,11 , persistent spin helices [12][13][14] , and the paradigmatic spin field-effect transistor 15,16 .…”