Splitting electronic spins with a Kondo double dot device

TL;DR

This paper proposes a quantum dot device exploiting the Kondo effect to generate two spatially separated, oppositely spin-polarized currents from a normal metal lead, functioning as an efficient spin filter.

Contribution

It introduces a simple double quantum dot setup that uses spin-orbital entanglement in the Kondo regime to achieve high-efficiency spin filtering with conductance reaching the quantum limit.

Findings

High efficiency spin filtering demonstrated in the Kondo regime

Device conductance reaches the unitary limit of e^2/h per spin branch

Spatial separation of spin-polarized currents achieved

Abstract

We present a simple device made of two small capacitively coupled quantum dots in parallel. This set-up can be used as an efficient "Stern-Gerlach" spin filter, able to simultaneously produce, from a normal metallic lead, two oppositely spin-polarized currents when submitted to a local magnetic field. Our proposal is based on the realization of a Kondo effect where spin and orbital degrees of freedom are entangled, allowing a spatial separation between the two spin polarized currents. In the low temperature Kondo regime, the efficiency is very high and the device conductance reaches the unitary limit, $\frac{e^2}{h}$ per spin branch.