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arXiv · 0908.1080

Lateral spin-orbit interaction and spin polarization in quantum point contacts

Anh T. Ngo·P. Debray·Sergio Ulloa
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Abstract

We study ballistic transport through semiconductor quantum point contact systems under different confinement geometries and applied fields. In particular, we investigate how the {\em lateral} spin-orbit coupling, introduced by asymmetric lateral confinement potentials, affects the spin polarization of the current. We find that even in the absence of external magnetic fields, a variable {\em non-zero spin polarization} can be obtained by controlling the asymmetric shape of the confinement potential. These results suggest a new approach to produce spin polarized electron sources and we study the dependence of this phenomenon on structural parameters and applied magnetic fields. This asymmetry-induced polarization provides also a plausible explanation of our recent observations of a 0.5 conductance plateau (in units of $2e^2/h$) in quantum point contacts made on InAs quantum-well structures. Although our estimates of the required spin-orbit interaction strength in these systems do not support this explanation, they likely play a role in the effects enhanced by electron-electron interactions.

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Anh T. Ngo, P. Debray, Sergio Ulloa. 2009-08-07. Lateral spin-orbit interaction and spin polarization in quantum point contacts. https://doi.org/10.1103/physrevb.81.115328

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