Lateral spin-orbit coupling (LSOC), resulting from the lateral in-plane electric field due to the confining potential inside a QPC, leads to a strongly spin-polarized current. The latter is created by purely electrical means in the absence of any applied magnetic field.

In the work, the team studied the appearance and evolution of several anomalous conductance plateaus (located within the range 0.4–0.7 G0 with G0 = 2e2/h) in InAlAs/InAs QPCs at T=4.2K, as a function of the offset bias between the two in-plane gates of the QPC.

The scientists found that the number and location of the anomalous conductance plateaus depend strongly on the polarity of the offset bias. The anomalous plateaus appear only over an intermediate range of offset bias of several volts. They are quite robust and broad. These results are interpreted as evidence for the sensitivity of the QPC spin polarization to defects (surface roughness and impurities [dangling bond]) generated during the etching process that forms the QPC side walls.

Even a very weak SOC can cause significant spin polarization provided the electron–electron interaction is very strong. Because GaAs has a very long spin coherence length (tens of microns at ambient temperature compared with tens of nanometers for InAs), it is an ideal candidate for developing all-electric spin devices operational far above 4.2K.

Work is underway to study single and dual GaAs QPC in the presence of LSOC towards the realization of an all-electrical spin valve operating at a few tens of Kelvin.

Further details can be found in the journal Nanotechnology.