Differential conductance and spin current in hybrid quantum dot-topological superconducting nanowire

Abstract

Majorana bound states (MBSs) are topologically protected and follow the non-abelian rather than the usual Fermi–Dirac statistical rule, and then are ideal choice for the preparation of quantum bits in topologically fault-tolerant quantum computing. The MBSs also have significant influences on the electron transport processes in mesoscopic systems and have been studied in the field of fabricating efficient and energy-saving quantum devices. In this study, we investigated electron transport through a hybridized system composed of a topological superconducting nanowire and quantum dot (QD). Effects of MBSs prepared at the nanowire on differential conductance are calculated and analyzed. It is proved that the differential conductance peak near the superconducting nanowires at zero bias reflects the existence of Majorana fermions. By using the Green's function equation of motion method, we found that a pure spin current without the accompany of charge current can be generated by changing the coupling strength between the QD and MBSs, as well as the accumulation of spin heat in the leads. In the presence of Coulomb interaction in the QD, the direction of pure spin current can be changed by modulating the dot energy level and the coupling strength between dot and MBSs.