Spin polarized current generation from quantum dots without magnetic fields

TL;DR

This paper demonstrates that unpolarized currents passing through chaotic quantum dots with spin-orbit coupling can generate significant spin polarization without magnetic fields, using random matrix theory to analyze the effect.

Contribution

It introduces a theoretical framework estimating spin polarization in quantum dots with spin-orbit coupling, highlighting the role of channel number, temperature, and dephasing.

Findings

RMS spin polarization up to 45% with specific channel configurations

Dephasing can enable spin polarization even with a single output channel

Finite temperature reduces the spin polarization effect

Abstract

An unpolarized charge current passing through a chaotic quantum dot with spin-orbit coupling can produce a spin polarized exit current without magnetic fields or ferromagnets. We use random matrix theory to estimate the typical spin polarization as a function of the number of channels in each lead in the limit of large spin-orbit coupling. We find rms spin polarizations up to 45% with one input channel and two output channels. Finite temperature and dephasing both suppress the effect, and we include dephasing effects using a new variation of the third lead model. If there is only one channel in the output lead, no spin polarization can be produced, but we show that dephasing lifts this restriction.