Zero-bias conductance peak in Majorana wires made of semiconductor/ superconductor hybrid structures

Abstract

Motivated by a recent experimental report Mourik claiming the likely observation of the Majorana mode in a semiconductor-superconductor hybrid structure, we study theoretically the dependence of the zero-bias conductance peak associated with the zero-energy Majorana mode in the topological superconducting phase as a function of temperature, tunnel barrier potential, and a magnetic field tilted from the direction of the wire for realistic wires of finite lengths. We find that higher temperatures and tunnel barriers as well as a large magnetic field in the direction transverse to the wire length could very strongly suppress the zero-bias conductance peak as observed in recent experiments. We also show that a strong magnetic field along the wire could eventually lead to the splitting of the zero bias peak into a doublet with the doublet energy splitting oscillating as a function of increasing magnetic field. Our results based on the standard theory of topological superconductivity in a semiconductor hybrid structure in the presence of proximity-induced superconductivity, spin-orbit coupling, and Zeeman splitting show that the recently reported experimental data are generally consistent with the existing theory that led to the predictions for the existence of the Majorana modes in the semiconductor hybrid structures in spite of some apparent anomalies in the experimental observations at first sight. We also make a prediction for the future observation of Majorana splitting in finite wires used in the experiments. © 2012 American Physical Society.