Andreev reflection at superconductor/2DEG interfaces inthe quantum Hall regime

摘要

We have experimentally studied the differential magnetoconductance of superconductor/rntwo-dimensional electron gas/superconductor (S/2DEG/S) and S/2DEGormalrnmetal junctions formed by superconducting NbN electrodes and a two-dimensional electronrngas (2DEG) in a high-mobility InGaAs/InP heterostructure. The differential conductance ofrnthe S/2DEG/S and S/2DEG/N junctions measured at zero magnetic field revealed featuresrncharacteristic to Andreev reflection at the interface. These features remain at high magneticrnfields. Measurements of the differential conductance across a S/2DEG junction with anrnadditional thin Au interlayer reveal a temperature-sensitive zero-bias conductance peak arisingrndue to Andreev reflection. We observed the conductance oscillations as a function ofrnmagnetic field at zero dc bias current in S/2DEG/S and S/2DEG/N junctions. At high dc biasrncurrents, the quantum Hall steps appear in the magnetic field dependence of the differentialrnconductance. Experimental results obtained can be qualitatively explained by taking Andreevrnreflection in high magnetic fields into account.