Majorana Fermions in Topological Superconducting Metallic Nanowires probed by a Superconducting Condensate

TL;DR

This study provides experimental evidence for Majorana fermions in superconducting lead nanowires, identified by zero bias conductance peaks under magnetic fields, indicating topological superconductivity in nanoscale systems.

Contribution

First experimental demonstration of Majorana fermions in superconducting nanowires using STM techniques and magnetic field tuning.

Findings

Zero bias conductance peaks observed under magnetic fields.

Topological superconducting state identified in nanowires.

Majorana fermions supported by conductance signatures.

Abstract

We report on several low temperature experiments supporting the presence of Majorana fermions in superconducting lead nanowires fabricated with a scanning tunneling microscope. These nanowires are the connecting bridges between the STM tip and the sample resulting from indentation processes. We show here that by a controlled tuning of the geometry of the nanowire region, in which superconductivity is confined by applied magnetic fields, the conductance curves obtained in these situations are indicative of topological superconductivity and Majorana fermions. The most prominent feature of this behavior is the emergence of a zero bias peak in the conductance curves, superimposed on a background characteristic of the conductance between a normal metal and a superconductor in the Andreev regime. The zero bias peak emerges in some nanowires when a magnetic field larger that the lead bulk critical field is applied. This field drives one of the electrodes into the normal state while the other, the tip, remains superconducting on its apex. Meanwhile a topological superconducting state appears in the connecting nanowire of nanometric size.