Magnetic-field dependence of Andreev reflection in a clean Nb-InAs-Nb junction

Abstract

The differential resistance in an InAs-inserted-channel ${\mathrm{In}}_{0.52}$${\mathrm{Al}}_{0.48}$As/${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$As heterostructure-coupled superconducting junction is enhanced within the Nb superconducting gap energy by applying a magnetic field. However, the enhancement saturates under a magnetic field of several mT. This behavior suggests the reduction of Andreev-reflection (AR) probabilities by the magnetic field. The AR probabilities are calculated as a function of the pair-potential penetration length into the InAs channel. The enhanced AR probabilities decrease with decreasing pair-potential penetration length. The magnetic field reduces the penetration of the pair potential in the channel and therefore reduces the AR probability. This reduction of AR probability causes an enhancement of dV/dI.