# Simple spin-orbit based devices for electron spin polarization

## TL;DR

This paper introduces simple quantum devices utilizing spin-orbit coupling without magnetic materials to achieve high electron spin polarization, with potential enhancement from structural curvature like in DNA.

## Contribution

It presents a novel device model based on coupled 1D chains with Rashba spin-orbit interaction, analyzing polarization effects and the influence of structural curvature and disorder.

## Key findings

- High polarization predicted in the proposed device model.
- Curvature, such as in DNA-like structures, enhances polarization.
- Disorder leads to a broad distribution of polarization, with potential for high polarization in specific realizations.

## Abstract

We propose quantum devices having spin-orbit coupling (but no magnetic fields or magnetic materials) that, when attached to leads, yield a high degree of transmitted electron polarization. An example of such a simple device is treated within a tight binding model composed of two 1D chains coupled by several consecutive rungs (i.e., a ladder) and subject to a gate voltage. The ensuing scattering problem (with Rashba spin-orbit coupling) is solved, and a sizable polarization is predicted. When the ladder is twisted into a helix (as in DNA), the curvature energy augments the polarization. For a system with random spin-orbit coupling, the distribution of polarization is broad, hence a high degree of polarization can be obtained in a measurement of a given disorder-realization. When disorder occurs in a double helix structure then, depending on scattering energy, the variance of the polarization distribution can increase even further due to helix curvature.