Phase-coherent quantum mechanical spin transport in a weakly disordered quasi-one-dimensional channel

Abstract

A transfer matrix technique is used to model phase coherent spin transport in the weakly disordered quasi one-dimensional channel of a gate-controlled electron spin interferometer [Datta and Das, Appl. Phys. Lett., 56, 665 (1990)]. It includes the effects of an axial magnetic field in the channel of the interferometer (caused by the ferromagnetic contacts), a Rashba spin-orbit interaction, and elastic (non-magnetic) impurity scattering. We show that in the presence of the axial magnetic field, non-magnetic impurities can cause spin relaxation in a manner similar to the Elliott-Yafet mechanism. The amplitudes and phases of the conductance oscillations of the interferometer, and the degree of spin-conductance polarization, are found to be quite sensitive to the height of the interface barrier at the contact, as well as the strength, locations and nature (attractive or repulsive) of just a few elastic non-magnetic impurities in the channel. This can seriously hinder practical applications of spin interferometers.

Rashba effect and magnetic field in semiconductor quantum wires

“…39 The effect of an in-plane magnetic field on the electron transport in quasi-1D systems has also been calculated. 40,41 In this work, we investigate the effect of a perpendicular magnetic field on the spectral and spin properties of a ballistic quantum wire with Rashba spin-orbit interaction. The results are twofold.…”

Digital switch and femtotesla magnetic field sensor based on Fano resonance in a spin field effect transistor

“…If we assume that the confinement potential in the z-direction is parabolic and given by V (z) = (1/2)m * ω 2 0 z 2 , then the approximate energy dispersion relations of the lowest spin split subbands in the channel (derived using perturbation theory) are given by [13,14,15]…”

Proposal for a dual-gate spin field effect transistor: A device with very small switching voltage and a large ON to OFF conductance ratio

“…Hereafter, we label these two configurations "ON" and "OFF" since they correspond to ON and OFF states of the transistor. Both in the ON and OFF states, T (E) contains several peaks and troughs due to Ramsauer and Fano resonances in the conductance of the channel, features which we have analyzed thoroughly in the past [6,7,8]. In the energy range [4198.5 -4200.5] meV, the transmission coefficient reaches unity several times when the SpinFET is biased in the ON configuration but is close to zero when biased in the complementary scheme.…”

“…This technique is fairly involved and the reader is referred to refs. [6,7,8] for the details. The results presented here are based on the assumption of the device parameters listed in Table I.…”

“…That results in considerable dynamic energy dissipation during switching. In contrast, our strategy is to modulate transmission resonances (Ramsauer and Fano-type resonances) that occur in the channel of traditional SpinFETs [6,7,8] with a gate potential. Since the resonance widths (in energy) are very small, a few mV change in the gate potential can take the device from on-resonance to off-resonance and switch it on or off.…”