Signatures of Majorana Fermions in Hybrid Superconductor-Semiconductor Nanowire Devices

TLDR

Majorana fermions, particles that are their own antiparticles, have been theoretically predicted to exist in topological superconductors. We performed electrical measurements on InSb nanowires contacted by a normal Au electrode and a superconducting NbTiN electrode, using gate voltages to tune electron density and form a tunnel barrier. In magnetic fields around 100 mT, we observed zero‑bias mid‑gap states that remained fixed despite changes in field and gate voltage, supporting the hypothesis of Majorana fermions.

Abstract

Majorana fermions are particles identical to their own antiparticles. They have been theoretically predicted to exist in topological superconductors. We report electrical measurements on InSb nanowires contacted with one normal (Au) and one superconducting electrode (NbTiN). Gate voltages vary electron density and define a tunnel barrier between normal and superconducting contacts. In the presence of magnetic fields of order 100 mT we observe bound, mid-gap states at zero bias voltage. These bound states remain fixed to zero bias even when magnetic fields and gate voltages are changed over considerable ranges. Our observations support the hypothesis of Majorana fermions in nanowires coupled to superconductors.