Electron waveguide interferometers for spin‐dependent transport experiments

Abstract

Semiconductor nanostructures are of interest in the field of spintronics, because they allow us to employ special features of low‐dimensional transport for spin polarization, manipulation, and detection. Proposals for spintronic devices are based on coherent transport and interference effects in extended electron waveguide (EWG) structures. We present the state‐of‐the‐art of low‐dimensional EWGs and Aharonov–Bohm (AB) interferometers, fabricated in GaAs/AlGaAs heterostructures. Low‐temperature measurements in etched quantum point contacts (QPCs) show large subband spacing and, in the presence of a source–drain DC bias, the differential conductance is resonantly enhanced due to a many‐body modification of the barrier potential because of spin fluctuations. Multiterminal asymmetric quantum wire rings (QRs) have been fabricated and AB conductance oscillations are used to detect electrostatically induced continuous phase shifts and ‐phase jumps, due to resonances and reflections at cross‐junctions. The effects of measurement configuration and non‐equilibrium in QR structures are also studied. By embedding a QPC into the leads of a QR, coherent mode‐filtered injection of electrons into a few‐mode AB interferometer is demonstrated. Single‐ and few‐mode spin transport in EWG interferometers is discussed and the opportunities offered by embedding quantum dots for studying interaction and spin effects are presented. The results encourage the investigation of spin‐dependent quantum transport in extended EWG interferometers.