Spin-relaxation anisotropy in asymmetrical (001)AlxGa1−xAsquantum wells from Hanle-effect measurements: Relative strengths of Rashba and Dresselhaus spin-orbit

Abstract

Spin relaxation of two-dimensional electrons in asymmetrical (001) AlGaAs quantum wells are measured by means of Hanle effect. Three different spin relaxation times for spins oriented along [110], [110] and [001] crystallographic directions are extracted demonstrating anisotropy of D'yakonov-Perel' spin relaxation mechanism. The relative strengths of Rashba and Dresselhaus terms describing the spin-orbit coupling in semiconductor quantum well structures. It is shown that the Rashba spin-orbit splitting is about four times stronger than the Dresselhaus splitting in the studied structure.PACS numbers: 73.21. Fg, 73.63.Hs, 72.25.Rb, 76.60.Jx Spintronics is at present time one of the most important areas of the semiconductor physics for both fundamental research and possible device applications [1]. The main problem of spintronics is creation, registration and lifetime control of carrier spin, especially in lowdimensional systems. Therefore investigation of spin relaxation processes is now an actual problem of the physics of semiconductor heterostructures.The main mechanism of spin relaxation in GaAs based quantum wells (QWs) is the D'yakonov-Perel' kinetic mechanism [2]. It is caused by lack of inversion centrum i) in the bulk semiconductor of which the system is made (bulk inversion asymmetry, or BIA), ii) in the heterostructure (structure inversion asymmetry, or SIA) and iii) in the chemical bonds at heterointerfaces (interface inversion asymmetry, or IIA) [2,3,4]. SIA can be caused by an external electric field or by deformation, BIA and IIA depend strongly on a size of carrier confinement. Therefore spin relaxation times can be controlled by gate voltage or by special heterostructure design.In Ref.[5], anisotropy of spin relaxation has been predicted for heterostructures grown along the axis [001]. It has been theoretically shown that lifetimes of spin oriented along the axes [110], [110] and [001] are different. In particular, changing relation between SIA and BIA one can achieve total suppression of relaxation for spin oriented along one of 110 axes. (IIA in (001)-grown structures is equivalent to BIA, therefore we will use a generalized term 'BIA' for both of them.) Detailed calculations [6,7,8] confirmed that spin relaxation anisotropy exists in real semiconductor heterostructures. Realization of such idea to control spin relaxation times gives new opportunities for spintronics [9]. However experimental discovery of this effect is missed so far.In this Letter, spin relaxation anisotropy in the plane of the QW is observed. In order to demonstrate this effect, the structure has been grown so that SIA and BIA are comparable in efficiency. Note that systems where both SIA and BIA take place have been studied in Refs. [10,11,12,13] but spin relaxation times have not been investigated in such structures.The D'yakonov-Perel' spin relaxation mechanism consists in electron spin precession around an effective magnetic field which is caused by lack of inversion centrum in the system. The corresponding Hamiltonia...

Experimental determination of the Rashba coefficient in InSb/InAlSb quantum wells at zero magnetic field and elevated temperatures

“…To understand this result we need to consider the nature of the Te doping in the two QWs. Recall that sample B is uniformly doped and therefore τ p = τ 1 = τ 3 , whereas for a modulation doped sample A we have τ p = τ 1 > τ 3 (we find τ p = τ 1 ≈ 5τ 3 ) [20,22]. Therefore, in the case of sample B an increased component of the momentum scattering perpendicular to the QW would bring into play the additional Dresselhaus term on the right hand side of Eq.…”

“…For sufficiently large ZFSS, spin relaxation is dominated by the D'yakonov-Perel (DP) process [16][17][18][19][20]. The DP process arises from fact that this spin-splitting, in contrast with the well known Zeeman splitting, corresponds to effective magnetic fields that are momentum dependent.…”

“…The DP spin relaxation rate for electrons at the Fermi energy (appropriate for a degenerately doped quantum well) which have been oriented along the [001] direction, appropriate for optical excitation is [17,20] …”

Spin dynamics in semiconductors

“…The interference of the two spin-orbit couplings leads to anisotropic spin splitting, which hence results in anisotropic spin precession [64][65][66][67], spin relaxation [194][195][196][197][198][199], spin diffusion [29,[32][33][34]37] and spin photocurrent [200][201][202]. Conversely, the ratio of β D /α R can be inferred from the anisotropy of spin precession [64,203], spin relaxation [198,199], spin diffusion [29,33] and spin photocurrent [200,201].…”

Rashba and Dresselhaus Couplings in Halide Perovskites: Accomplishments and Opportunities for Spintronics and Spin–Orbitronics

“…The working principle of those approaches is to modify the splitting through an external stimulus being a static electric field, 88,89 a transverse static magnetic field (Hanle effect) 90,91 or in transmission with an oscillating magnetic field (time-resolved Faraday rotation). 92 All these alternatives are possible in HOP, since external electric and magnetic fields have already been applied with success on HOP to investigate various effects such as the influence on excitons.…”