A quantum point contact as a (near) perfect spin polariser

Abstract

In this paper, I present a simple method of obtaining spin-polarised current from a QPC with a large Rashba interaction. The origin of this spin polarisation is the adiabatic evolution of spin "up" of the first QPC sub-band, into spin "down" of the second QPC sub-band. Unique experimental signatures of this effect can be obtained using a magnetic focusing setup, with the characteristic "double" peak of spin-split magnetic focusing only present for conductances $G>2e^2/h$. These particular magnetic focusing features are present in recently publish experimental results. Finally, I consider hole QPCs, where due to the particular kinematic structure of the Rashba interaction, the required parameters are much less favourable for experimental realisation.