Spin Polarization at Semiconductor Point Contacts in Absence of Magnetic Field

TL;DR

This paper demonstrates that semiconductor point contacts with spin-orbit interaction can generate significant spin-polarized currents without magnetic fields, with conductance quantization and high polarization ratios shown through numerical analysis.

Contribution

It reveals that spin polarization can be achieved in semiconductor point contacts solely via spin-orbit interaction, without magnetic materials or fields, and quantifies the conditions for high polarization.

Findings

Conductance is quantized in units of 2e^2/h unless SO interaction is too strong.

Current is spin-polarized in the transverse direction.

More than 50% spin polarization can be achieved with accessible SO interaction strengths.

Abstract

Semiconductor point contacts can be a useful tool for producing spin-polarized currents in the presence of spin-orbit (SO) interaction. Neither magnetic fields nor magnetic materials are required. By numerical studies, we show that (i) the conductance is quantized in units of 2e^2/h unless the SO interaction is too strong, (ii) the current is spin-polarized in the transverse direction, and (iii) a spin polarization of more than 50% can be realized with experimentally accessible values of the SO interaction strength. The spin-polarization ratio is determined by the adiabaticity of the transition between subbands of different spins during the transport through the point contacts.