Engineering the spin polarization of one-dimensional electrons

C Yan,D Ritchie,S Kumar,K Thomas,I Farrer,M Pepper,G Jones,P See,J Griffiths

doi:10.1088/1361-648x/aaa7ce

Abstract

We present results of magneto-focusing on the controlled monitoring of spin polarization within a one-dimensional (1D) channel, and its subsequent effect on modulating the spin–orbit interaction (SOI) in a 2D GaAs electron gas. We demonstrate that electrons within a 1D channel can be partially spin polarized as the effective length of the 1D channel is varied in agreement with the theoretical prediction. Such polarized 1D electrons when injected into a 2D region result in a split in the odd-focusing peaks, whereas the even peaks remain unaffected (single peak). On the other hand, the unpolarized electrons do not affect the focusing spectrum and the odd and even peaks remain as single peaks, respectively. The split in odd-focusing peaks is evidence of direct measurement of spin polarization within a 1D channel, where each sub-peak represents the population of a particular spin state. Confirmation of the spin splitting is determined by a selective modulation of the focusing peaks due to the Zeeman energy in the presence of an in-plane magnetic field. We suggest that the SOI in the 2D regime is enhanced by a stream of polarized 1D electrons. The spatial control of spin states of injected 1D electrons and the possibility of tuning the SOI may open up a new regime of spin-engineering with application in future quantum information schemes.

Highlights

We found that a large spin-orbit interaction (SOI)
The devices studied in the present work were fabricated from the high mobility two dimensional electron gas (2DEG) formed at the interface of
Hall effect and Shubnikov-de Haas (SdH) oscillations are negligible in the regime of focusing[18], and all the features are due to transverse electron focusing only

Summary

Introduction

Ac enhancement in the SOC may be seen by measuring the split in of focusing peaks. The devices studied in the present work were fabricated from the high mobility two dimensional electron gas (2DEG) formed at the interface of. (a)-(c) show the focusing results as a function of injector conductance for 90◦ , 60◦ and 30◦ QPC, respectively. By biasing the injector and detector independently and symmetrically, we made sure that a lateral electric field across the quasi-1D injector channel was not present as this could affect the focussing process, for instance resulting in a shift of focusing peaks due to the change of the effective separation between injector and detector. The effect was reproducible in different samples and in different focusing device geometries

Results and discussion

Robustness of peak splitting ce

In-plane magnetic field dependence

Conclusion ce