Quantum transport through a quantum dot structure side coupled with many quantum-dot and Majorana-bound-state pairs

Abstract

We theoretically investigate the electron transport properties of a wheel-like quantum dot (QD) structure with a central QD side coupled with many pairs of QD and Majorana bound states (MBSs) by using the nonequilibrium Green’s function method. For clarity, we concentrate our researches on the parameter regime where interdot couplings is much smaller than the inter-MBS and MBS-QD couplings, which ensures the conductance peaks induced by them distinguishable. In the absence of the interdot couplings among the side QDs, the increase of the MBS-QD pair number is equivalent to the increase of the interdot coupling in the QD structure including one central QD and one MBS-QD pair. It is shown that as a response the interval between two side symmetrical peaks will be enlarged, and the MBS-QD couplings will bring into being a zero-bias conductance peak which can be split into two symmetrical sub-peaks by the nonzero inter-MBS couplings. In the presence of the interdot couplings among the side QDs, they make serious influences on the conductance peaks determined by the QD energy levels, and still comes into being the zero-bias conductance peak due to the MBS-QD couplings, yet which is split into two asymmetrical sub-peaks under the influences of the nonzero inter-MBS couplings. Moreover, we conduct a detailed investigation into how the couplings among side QDs affect the transport properties, clearly exposing the underneath mechanics responsible for producing these phenomena. Finally, a generalization is made so as to discuss the geometry universality and the parameter universality of the conclusion drawn in the present work. It should be emphasized that this research will be helpful for a comprehensive understanding the quantum transport through the QD systems coupled with MBSs.