Fraction conductivity induced by a Majorana zero mode in a nanomagnet

Abstract

In mesoscopic devices, the spin-resolved transport physics induced by Majorana zero mode (MZM) has attracted much attention. Here we study a system consisting of a quantum dot coupled to metallic leads and side-coupled to a local large spin and a topological superconductor wire hosting MZMs. The interplay of MZM and impurity (local large spin) is investigated. By using Hubbard operator Green’s function method, we obtain an analytical result for retarded Green’s function with finite U. Then we find that in the case of on-resonance and zero Coulomb interaction, the 1/2 signature of MZM at zero energy survives, but the number of peaks in spectral function is dependent on the local large spin. When S = integer, the peak numbers are 2S+3; when S = half-integer, the numbers are 2S+2. Moreover, fraction conductivity arises in the charge conductance at zero energy for S = integer. When Coulomb correlation arises, the peak numbers and heights in conductance are affected, and the MZM-induced symmetry of conductance peaks around zero energy is also destroyed. Our work shows that the interplay of local large spin and MZM generates some interesting results, which may provide additional fingerprints for the detection of MZM.