Andreev reflection and cyclotron motion at superconductor-normal-metal interfaces

We investigate Andreev reflection at the interface between a superconductor and a two-dimensional electron system (2DES) in an external magnetic field such that cyclotron motion is important in the latter. A finite Zeeman splitting in the 2DES and the presence of diamagnetic screening currents in the superconductor are incorporated into a microscopic theory of Andreev edge states, which is based on the Bogoliubov-de Gennes formalism. The Andreev-reflection contribution to the interface conductance is calculated. The effect of Zeeman splitting is most visible as a double-step feature in the conductance through clean interfaces. Due to a screening current, conductance steps are shifted to larger filling factors and the formation of Andreev edge states is suppressed below a critical filling factor.