Mesoscopic Stern-Gerlach spin filter by nonuniform spin-orbit interaction

Abstract

A novel spin filtering in two-dimensional electron system with nonuniform spin-orbit interactions (SOI) is theoretically studied. The strength of SOI is modulated perpendicular to the charge current. A spatial gradient of effective magnetic field due to the nonuniform SOI causes the Stern-Gerlach type spin separation. The direction of the polarization is perpendicular to the current and parallel to the spatial gradient. Almost 100 % spin polarization can be realized even without applying any external magnetic fields and without attaching ferromagnetic contacts. The spin polarization persists even in the presence of randomness.Considerable attention has been devoted to the manipulation of the electron spin in semiconductor systems. 1,2 To control the spin of electrons in semiconductors, the spin-orbit interaction (SOI) due to the lack of the inversion symmetry in two dimensional electron system (2DES) is quite useful since its strength can be controlled by an additional gate voltage. 3,4 The spin field-effect transistor proposed by Datta and Das is a hybrid structure of ferromagnetic electrodes (FM) and a semiconductor (SM) 2DES channel. 5 This hybrid device, however, requires a complex and careful fabrication process. Furthermore, spin injection efficiency from FM into SM is poor because of a conductance mismatch between FM and SM. 6 Therefore, it is desired that spin polarized carriers in semiconductor channels can be generated and manipulated without attaching any ferromagnetic contacts and without applying any external magnetic fields. Several devices based on the SOI are proposed to have spin polarized carriers in semiconductor channel. 7,8,9,10,11,12,13 From experimental point of view, the spin polarization mechanism should be robust against disorder.One of the historical experiments of the spin separation is the Stern-Gerlach experiment. 14 They have considered a particle with spin propagating through the nonuniform magnetic field. Because the derivative of the magnetic field plays a role of the spin-dependent potential, particles with up and down spins are accelerated in opposite directions. However, for electrons, this effect is hard to observe because of the effect of the Lorentz force acting on a electron beam in transverse directions. 15 The importance of the modulated SOI on the transport properties has recently been stressed. 16,17,18,19,20 Since the effect of SOI on the propagating electrons is, in some respect, similar to the effective magnetic field, the modulated SOI is expected to cause the Stern-Gerlach like spin separation. In this paper, we theoretically demonstrate that a mesoscopic Stern-Gerlach spin filter is feasible by using a nonuniform spin-orbit interaction as shown in Fig. 1. The strength of the SOI is modulated along the direction perpendicular to the charge current. We demonstrate that nearly 100% spin polarization (perpendicular both to the current and the direction normal to 2DES) can be achieved without a ferromagnetic contact and an external magnetic field. The above results a...

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

“…It has been proposed to use the electric control of spins to build a Stern-Gerlach spin-filter without ferromagnetic materials. 122 An important contribution has been delivered by Datta and Das, who proposed to use this property to built a spin field effect transistor (spin-FET, Figure 4-b). 123 Because spins precess under the influence of the effective magnetic A c c e p t e d m a n u s c r i p t field induced by the Rashba/Dresselhaus effects, and because their amplitude can be tuned by a gate voltage, one can control the pace of the spin precession and finally control the orientation of the spin when it reaches drain.…”

“…It has been proposed to use the electric control of spins to build a Stern-Gerlach spin-filter without ferromagnetic materials. 122 An important contribution has been delivered by Datta and Das, who proposed to use this property to built a spin field effect transistor (spin-FET, Figure 4-b). 123 Because spins precess under the influence of the effective magnetic …”

Rashba effect and magnetic field in semiconductor quantum wires

“…7,8,9,10 This is the basis of the spin dependent field-effect-transistor (spinFET) earlier discussed theoretically by Datta and Das. 11 Numerous theoretical spintronic devices have been proposed using interference, 12,13,14,15 resonant tunneling, 16,17,18,19 ferromagnet-semiconductor hybrid structures, 20,21,22,23 multiterminal geometries, 24,25,26,27 and adiabatic pumping. 28 Magnetic field effects on the transport properties in 2D systems with SOI have been investigated theoretically 29,30,31 as well as experimentally 7,8,9,10,32,33 .…”

Weak antilocalization in high mobilityGaxIn1−xAs∕InPtwo-dimensional

“…1,2,3 These properties are essential for the realization of various spintronic devices, e.g., spin field effect transistors, 4,5 spin-filters, 6,7 or spin-splitters. 8 The strength of the Rashba coupling can be estimated from measurements of Shubnikov-de Haas oscillations by analyzing the characteristic beating pattern. 1,2,3 However, the latter can also be evoked by inhomogeneities of the sheet carrier concentration 9,10 or due to a slightly occupied second lowest subband; 11 thus, the observance of a beating pattern is not an unambiguous indication of the presence of spin-orbit coupling.…”