Observation of Majorana Fermions in Ferromagnetic Atomic Chains on a Superconductor

TL;DR

This study demonstrates the creation of one-dimensional topological superconductors using ferromagnetic Fe atomic chains on Pb, providing experimental evidence for Majorana fermions at the chain ends through spectroscopic imaging.

Contribution

The paper reports the first direct observation of Majorana fermions in ferromagnetic atomic chains on a superconductor, advancing topological quantum matter research.

Findings

Zero energy end states observed at chain edges

Superconductivity induces a gap in Fe chains

Evidence supports topological phase formation

Abstract

Majorana fermions are predicted to localize at the edge of a topological superconductor, a state of matter that can form when a ferromagnetic system is placed in proximity to a conventional superconductor with strong spin-orbit interaction. With the goal of realizing a one-dimensional topological superconductor, we have fabricated ferromagnetic iron (Fe) atomic chains on the surface of superconducting lead (Pb). Using high-resolution spectroscopic imaging techniques, we show that the onset of superconductivity, which gaps the electronic density of states in the bulk of the Fe chains, is accompanied by the appearance of zero energy end states. This spatially resolved signature provides strong evidence, corroborated by other observations, for the formation of a topological phase and edge-bound Majorana fermions in our atomic chains.