Stern-Gerlach effect and spin separation in InGaAs nanstructures

The demonstration of quantized spin splitting by Stern and Gerlach in 1922 is one of the most important experiments in modern physics. We utilized an effective non-uniform magnetic field which originates from Rashba spin orbit interaction (SOI) and demonstrated an experimental manifestation of electronic Stern-Gerlach spin separation in InGaAs based quantum point contacts (QPCs) [1]. Lateral potential confinement in a trench-type QPC creates a spatial modulation of Rashba SOI inducing a spin dependent force Clear conductance plateaus are observed in steps of 2$e^{\mathrm{2}}$/$h $when the strength of Rashba SOI becomes small. However, when the Rashba SOI is enhanced by applying the top gate, a half-integer plateau additionally appears at 0.5(2$e^{2}/h)$, indicating the spin polarized current. We found that the spin polarization of the conduction electrons in this plateau is as high as 70{\%}. Our new approach for generating spin polarization in semiconductor nanostructures provides a way to seamlessly integrate electrical spin generation, manipulation, and detection in a single semiconductor device without the need for either external magnetic fields or magnetic materials. \\[4pt] [1] M. Kohda \textit{et al}. Nature Communications 3, 1082 (2012).