Study of spin polarization and spin-related transport in quantum point contacts coupled through a two-dimensional...

Quantum wires and quantum point contacts (QPCs) have been realized in GaAs/AlGaAs heterostructures, where a two-dimensional electron gas (2DEG) resides at the interface between the GaAs and AlGaAs layered semiconductors. This paper presents a theoretical study of electron transport in a device composed of two QPCs connected via a wider two-dimensional (2D) region. The QPCs, defined by split gates, serve as injector and detector of electrons, while the intermediate 2D region the two QPCs can be electrostatically tuned by a top gate. Electron transport is modeled using density functional theory. Experimental observations suggest that, when the injector QPC is asymmetrically biased, the broadening of the current peak detected at the detector QPC may be associated with spin polarization in the injector. Our simulations for both symmetric and asymmetric injector QPCs indicate that the shape of detector current profile does not strongly depend on injector's asymmetry, however the width of the current distribution varies with the current through injector QPC. This variation is consistent with the presence of spin-related effects, such as the0.7(2e2/h)conductance anomaly observed in the injector QPC. These results provide insight into the electronic property of 2DEG in the proposed device and may be useful for the future design of semiconductor structures for spintronics and quantum device applications.