Majorana Fermions in Semiconductor Nanowires

TL;DR

This paper investigates how multiband semiconductor nanowires coupled with superconductors can host Majorana fermions, highlighting conditions that favor their stability and experimental detection, thus advancing solid-state topological quantum computing.

Contribution

It demonstrates that multiband occupancy enhances the stability of topological superconducting phases and provides detailed analysis of experimental conditions for Majorana fermion realization.

Findings

Multiband nanowires support higher carrier densities and stabilize Majorana modes.

Disorder effects on topological phase stability are characterized.

Predicted experimental signatures include zero-bias conductance peaks.

Abstract

We study multiband semiconducting nanowires proximity-coupled with an s-wave superconductor and calculate the topological phase diagram as a function of the chemical potential and magnetic field. The non-trivial topological state corresponds to a superconducting phase supporting an odd number of pairs of Majorana modes localized at the ends of the wire, whereas the non-topological state corresponds to a superconducting phase with no Majoranas or with an even number of pairs of Majorana modes. Our key finding is that multiband occupancy not only lifts the stringent constraint of one-dimensionality, but also allows having higher carrier density in the nanowire. Consequently, multiband nanowires are better-suited for stabilizing the topological superconducting phase and for observing the Majorana physics. We present a detailed study of the parameter space for multiband semiconductor nanowires focusing on understanding the key experimental conditions required for the realization and detection of Majorana fermions in solid-state systems. We include various sources of disorder and characterize their effects on the stability of the topological phase. Finally, we calculate the local density of states as well as the differential tunneling conductance as functions of external parameters and predict the experimental signatures that would establish the existence of emergent Majorana zero-energy modes in solid-state systems.