Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures

Shun-Tsung Lo,G L Creeth,I Farrer,M Pepper,G A C Jones,D A Ritchie,Tse-Ming Chen,Ju-Chun Fan,Chin-Hung Chen,H E Beere,J P Griffiths,L W Smith,Che-Wei Chang

doi:10.1038/ncomms15997

Abstract

The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Here we demonstrate that the spatial spin splitting of a coherent beam of electrons can be achieved and controlled using the interplay between an external magnetic field and Rashba spin–orbit interaction in semiconductor nanostructures. The technique of transverse magnetic focusing is used to detect this spin separation. More notably, our ability to engineer the spin–orbit interactions enables us to simultaneously manipulate and probe the coherent spin dynamics of both spin species and hence their correlation, which could open a route towards spintronics and spin-based quantum information processing.

Highlights

The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time
A quantum point contact (QPC)—a one-dimensional (1D) constriction created by applying voltages to split gates patterned on the surface of an InGaAs heterostructure—is used to inject an unpolarized electron beam into a two-dimensional electron gas (2DEG)
The 2DEG is formed in the InGaAs quantum well (Methods section), wherein the structural inversion asymmetry of the well generates a momentum-dependent magnetic field BSRO on the spin of every moving electron, the so-called Rashba spin–orbit interaction

Summary

Introduction

The spatial separation of electron spins followed by the control of their individual spin dynamics has recently emerged as an essential ingredient in many proposals for spin-based technologies because it would enable both of the two spin species to be simultaneously utilized, distinct from most of the current spintronic studies and technologies wherein only one spin species could be handled at a time. Spin-up and spin-down electrons have different momenta and when moving through a magnetic field, will experience different Lorentz forces and undergo different cyclotron motions This concept has been successfully demonstrated, using a hole gas in which the spin–orbit interaction was not tunable[11,12,13], but to manipulate and study the behaviour of the spatially separated spins remains an outstanding challenge. The spatial separation, coherent spin dynamics and phase correlation between the up- and down-spin electrons can all be—electrically and on-chip—controlled and probed This allows both of two spin types (instead of just the majority one as in most previous studies) to be simultaneously probed and manipulated, which promises to advance spintronic technologies that require both spin types to be operated together

Methods

Results

Conclusion