Transport properties of semiconductor-superconductor junctions in quantizing magnetic fields

Abstract

We present the results of a numerical calculation on the quantum transport properties in junctions of a two-dimensional electron gas and a superconductor in the presence of a perpendicular magnetic field. The low-field conductance drops in a steplike manner, whenever the Landau levels are depopulated, provided that quasiparticle excitations are almost perfectly Andreev reflected from the interface. If the normal reflection is enhanced, the conductance exhibits a sinusoidal oscillation. In contrast to the behavior in conventional conductors, the maxima of the oscillation take place at the depopulation thresholds. In high magnetic fields, a periodic transmission resonance with a complete disappearance of the conductance is found, irrespective of the Andreev-reflection probability. The current distribution indicates that this high-field oscillation is ascribed to the skipping orbit along the interface. We show that the plateau value in the Hall resistance remains unchanged when one of the leads is replaced by the superconductor. Using the selective edge-state detection technique, the distribution of Andreev-reflected quasiparticles among the edge states can be evaluated.