Electrical transport through a quantum dot side-coupled to a topological superconductor

Abstract

We propose to measure the differential conductance $G$ as a function of the bias $V$ for a quantum dot side-coupled to a topological superconductor to detect the existence of the chiral Majorana edge states. It turns out that $G$ for the spinless dot is an oscillatory (but not periodic) function of $eV$ due to the coupling to the chiral Majorana edge states, where $-e$ is the charge carried by the electron. The behavior of $G$ versus $eV$ is distinguished from the one for a multi-level dot in three respects. First of all, due to the coupling to the topological superconductor, the value of $G$ will shift upon adding or removing a vortex in the topological superconductor. Next, for an off-resonance dot, the conductance peak in the present case takes a universal value $e^2/(2h)$ when the two leads are symmetrically coupled to the dot. Finally, for a symmetric setup and an on-resonance dot, the conductance peak will approach the same universal value $e^2/(2h)$ at large bias.