Microscopic theory of spin‐filtering in non‐magnetic semiconductor nanostructures

Abstract

In this paper, we investigate the intrinsic spin‐Hall effect in mesoscopic systems, i.e. spin‐orbit induced spin‐polarizations with and without external magnetic fields in confined two‐dimensional systems at low temperatures. We employ a non‐equilibrium Green's function approach that takes into account the coupling of non‐equilibrium spin occupancies and spin‐resolved electronic scattering states in open nanometer quantum systems. Importantly, our calculations go beyond the widely used continuum approximation of the spin‐orbit interaction in the envelope function approximation and are based on a microscopic relativistic tight‐binding approach that ensures the spin‐orbit effects to be properly taken into account for any degree of charge confinement and localization and to all orders in the electron wave vector. We show that the qualitative trends and results in spin polarizations, their dependency on charge density, spin‐orbit interaction strength, and confinement, as obtained within the envelope function approximation, agree with the results of atomistic calculations. The quantitative results, on the other hand, can differ significantly. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Spin‐Hall effect and spin coherent waves in semiconductors with Rashba spin‐orbit interaction

“…The detailed consideration of the complex valence band structure is a challenging task that requires extensive numerical work. However, as shown recently [5], principle results of such an approach are in qualitative agreement with the k · p envelope function theory. In order to derive analytical results that capture some main physical properties of the system, we adopt, therefore, the simple cubic Rashba model for the description of the SOI.…”

Highly Transparent Contacts to the 1D Hole Gas in Ultrascaled Ge/Si Core/Shell Nanowires

“…Cooling the sample does not change the overall conductance, but at T = 150 K and even more pronounced for lower temperatures, distinctive plateau-like features can be observed. As the channel length of this particular device is below the scattering mean free path in Ge/Si core/shell NWs of 70 nm, we associate this quantization of conductance in steps of G 0 = 2 e 2 / h with one-dimensional spin-degenerate sub-band-resolved quantum ballistic transport. ,, Given that the Ge/Si core/shell segment is in the ballistic limit and that we are in a linear regime, we can estimate the transparency of the interface by linearly fitting R = ( R 0 + R I )/ n , blue curve of the inset, where R 0 = h /2 e 2 is the quantized resistance and R I = R 0 (1 – T )/ T is the interface resistance due to scattering. In the inset the resistance ( R = 1/ G ) of the plateaus taken at the points marked by black arrows are plotted against the inverse of the conducting channel number, associated with that plateau (1/ n ).…”