Spin-polarized electric currents in quantum transport through tubular two-dimensional electron gases

TL;DR

This paper develops a theoretical framework using scattering theory to analyze spin and charge currents in a tubular two-dimensional electron gas with spin-orbit interactions, revealing quantized conductance steps with spin polarization.

Contribution

It introduces a Landauer-type formula for spin and charge currents in systems with spin-orbit coupling and applies it to a cylindrical geometry, highlighting unique spin polarization effects.

Findings

Quantized conductance steps are split into two in the presence of boundary scattering.

New conductance steps exhibit non-zero spin conductance.

Spin polarization is perpendicular to the current direction.

Abstract

Scattering theory is employed to derive a Landauer-type formula for the spin and the charge currents, through a finite region where spin-orbit interactions are effective. It is shown that the transmission matrix yields the spatial direction and the magnitude of the spin polarization. This formula is used to study the currents through a tubular two-dimensional electron gas. In this cylindrical geometry, which may be realized in experiment, the transverse conduction channels are not mixed (provided that the spin-orbit coupling is uniform). It is then found that for modest boundary scattering, each step in the quantized conductance is split into two, and the new steps have a non-zero spin conductance, with the spin polarization perpendicular to the direction of the current.