Transverse currents in spin transistors

TL;DR

This paper demonstrates the presence of transverse currents in Datta-Das spin transistors with ferromagnetic leads and spin-orbit coupling, revealing oscillatory behavior and nonzero transverse conductivities even when longitudinal conductance is suppressed.

Contribution

It uncovers the existence of transverse currents in spin transistors with spin-orbit coupling, showing their dependence on magnetization direction and measurement location, and analyzing their behavior under different system widths.

Findings

Transverse conductivities depend on ferromagnet polarization and measurement position.

Conductivities exhibit Fabry-Pérot oscillations with varying spin-orbit region length.

Transverse conductivities remain nonzero even when longitudinal conductance is suppressed.

Abstract

In many systems, planar Hall effect wherein transverse signal appears in response to longitudinal stimulus is rooted in spin-orbit coupling. A spin transistor put forward by Datta and Das on the other hand consists of ferromagnetic leads connected to spin-orbit coupled central region and its conductance can be controlled by tuning the strength of spin-orbit coupling. We find that transverse currents also appear in Datta-Das transistors made by connecting two two-dimensional ferromagnetic reservoirs to a central spin-orbit coupled two-dimensional electron gas. We find that the spin transistor exhibits a nonzero transverse conductivity which depends on the direction of polarization in ferromagnets and the location where it is measured. We study the conductivities for the system with finite and infinite widths. The conductivities exhibit Fabry-P\'erot type oscillations as the length of the spin-orbit coupled regions is varied. Interestingly, even in the limit when longitudinal conductivity is made zero by cutting off the junction between the central spin-orbit coupled region and the ferromagnetic lead on one side (right), the transverse conductivities remain nonzero in the regions that are on the left side of the cut-off junction.