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The magnetoresistance at temperatures below 20 K in an n-InSb/ In 0.85 Al 0.15 Sb two-dimensional electron system is studied and described in terms of antilocalization due to quantum interference under strong spin-orbit interaction. The spin-orbit interaction coefficients are extracted by fitting the magnetoresistance data to an antilocalization theory distinguishing the Rashba and Dresselhaus contributions. A good agreement between magnetoresistance data and theory suggests a Rashba coefficient ͉␣͉Ϸ0.03 eV Å and a Dresselhaus coefficient ␥ Ϸ 490 eV Å 3 . A strong contribution from the Dresselhaus term leads to pronounced anisotropy in the energy splitting induced by spin-orbit interaction in the two-dimensional electron dispersion.

A mesoscopic nonmagnetic magnetoresistive read-head sensor based on the recently reported extraordinary magnetoresistance (EMR) effect has been fabricated from a narrow-gap Si-doped InSb quantum well. The sensor has a conservatively estimated areal-density of 116 Gb/in.2 with a 300 K EMR of 6% and a current sensitivity of 147 Ω/T at a relevant field of 0.05 T and a bias of 0.27 T. Because this sensor is not subject to magnetic noise, which limits conventional sensors to areal densities of order 100 Gb/in.2, it opens a pathway to ultra-high-density recording at areal densities of order 1 Tb/in.2.

We use electron spin resonance in the far infrared to probe the Landau-level spin splitting in symmetric and asymmetric InSb quantum wells. The asymmetric wells exhibit a strong deviation in behavior from the symmetric wells at low magnetic fields with apparent g factors far in excess of the bulk g factor of InSb. These asymmetry-induced shifts in the spin resonance depend on Landau-level The study of electron spin phenomena in semiconductor heterostructures has intensified dramatically in recent years. The field, "spintronics" has emerged with the purpose of developing devices combining the charge and spin degrees of freedom. In particular, spin splitting caused by bulk inversion asymmetry and structural inversion asymmetry (SIAoften called Rashba splitting) has attracted much attention. Understanding the spin-orbit interaction caused by SIA, which is predicted to lead to spin splitting even without an applied magnetic field, 1,2 is important for developing spinbased devices. To date, experimental evidence for Rashba splitting in two-dimensional electron systems (2DESs) has been chiefly confined to the observed beating of Shubnikov-de Haas (SdH) oscillations 3,4 that is presumed to arise from different populations of electron spin orientations. This beating has been interpreted in a number of heterostructures [3][4][5][6][7][8][9][10][11][12][13][14][15][16] to deduce the Rashba parameter ␣, which is expected to depend on materials parameters and the electric field. The zero-field spin splitting has also been inferred from Raman-scattering spectra 17 in GaAs and weak anti-localization measurements in InGaAs quantum wells 18 . In this paper, we report on electron spin resonance (ESR) experiments on 2DESs in InSb quantum wells. By observing transitions between states with the same Landau level index but opposite spin orientations, we directly measure the spin splitting as a function of applied magnetic field B. In addition to the B = 0 spin splitting, the Rashba model 1 predicts considerable modification of the Landau-level energy structure at nonzero B for asymmetric heterostructures, which has not been previously confirmed. Because of the large effective g factor and large predicted Rashba effect, 6 the spin splitting in InSb-based 2DESs should occur at far infrared frequencies for B Ͻ 10 T. Our experiments demonstrate that the Rashba effect is relatively strong in InSb quantum wells and that ESR is a powerful technique for studying the Rashba effect.Our samples are InSb single quantum wells of widths 30 and 20 nm with Al 0.09 In 0.91 Sb barrier layers that are ␦ doped with Si. The Si ␦ layers are located either singly on one side of the quantum well (asymmetric samples) or equidistant on both sides of the quantum well (symmetric samples). The ␦-doped layers within the barrier layers are typically located 70 nm from the well center. The barrier layers on the substrate and surface sides of the wells are 3 m and 160 nm thick, respectively. Silicon dopants are placed near the surface to limit surface depletion. ...

We present a method to create spin-polarized beams of ballistic electrons in a twodimensional electron system in the presence of spin-orbit interaction. Scattering of a spinunpolarized injected beam from a lithographic barrier leads to the creation of two fully spin-polarized side beams, in addition to an unpolarized specularly reflected beam.Experimental magnetotransport data on InSb/InAlSb heterostructures demonstrate the spin-polarized reflection in a mesoscopic geometry, and confirm our theoretical predictions.