Semiconductor few-electron quantum dot operated as a bipolar spin filter

TL;DR

This paper demonstrates a quantum dot device that acts as an electrically tunable bipolar spin filter by exploiting Zeeman splitting in few-electron states under a strong magnetic field.

Contribution

It introduces a quantum dot-based bipolar spin filter and shows that higher-order processes and spin-orbit interactions minimally affect its polarization.

Findings

Zeeman splitting observed in two-electron triplet states

Spin polarization is opposite at different electron transitions

Device functions as a tunable bipolar spin filter

Abstract

We study the spin states of a few-electron quantum dot defined in a two-dimensional electron gas, by applying a large in-plane magnetic field. We observe the Zeeman splitting of the two-electron spin triplet states. Also, the one-electron Zeeman splitting is clearly resolved at both the zero-to-one and the one-to-two electron transition. Since the spin of the electrons transmitted through the dot is opposite at these two transitions, this device can be employed as an electrically tunable, bipolar spin filter. Calculations and measurements show that higher-order tunnel processes and spin-orbit interaction have a negligible effect on the polarization.