Resonant Andreev reflection in a normal-metal/quantum-dot/superconductor system with coupled Majorana bound states**Project supported by the National Natural Science Foundation of China (Grant Nos. 61176089 and 10974043), the Natural Science Foundation of Hebei Province, China (Grant Nos. A2011205092 and 2014205005), and the Fund for Hebei Normal University for Nationalities, China (Grant No. 201109).

Abstract

Andreev reflection (AR) in a normal-metal/quantum-dot/superconductor (N–QD–S) system with coupled Majorana bound states (MBSs) is investigated theoretically. We find that in the N–QD–S system, the AR can be enhanced when coupling to the MBSs is incorporated. Fano line-shapes can be observed in the AR conductance spectrum when there is an appropriate QD–MBS coupling or MBS–MBS coupling. The AR conductance is always e2/2h at the zero Fermi energy point when only QD–MBSs coupling is considered. In addition, the resonant AR occurs when the MBS–MBS coupling roughly equals to the QD energy level. We also find that an AR antiresonance appears when the QD energy level approximately equals to the sum of the QD–MBS coupling and the MBS–MBS coupling. These features may serve as characteristic signatures for the probe of MBSs.