Yu-Shiba-Rusinov bands in a self-assembled kagome lattice of magnetic molecules

TL;DR

This study demonstrates the creation of a magnetic kagome lattice on a superconducting substrate using molecular self-assembly, revealing Yu-Shiba-Rusinov bands that could host exotic quantum states.

Contribution

It introduces a method to realize a magnetic kagome lattice on a superconductor, enabling the study of protected YSR bands and potential correlated quantum phases.

Findings

YSR states are observed inside the superconducting gap.

Extended YSR bands form in the kagome lattice.

The kagome bands are protected within the superconducting gap.

Abstract

Kagome lattices constitute versatile platforms for studying paradigmatic correlated phases. While molecular self-assembly of kagome structures on metallic substrates is promising, it is challenging to realize pristine kagome properties because of hybridization with the bulk degrees of freedom and modified electron-electron interactions. We suggest that a superconducting substrate offers an ideal support for a magnetic kagome lattice. Exchange coupling induces kagome-derived bands at the interface, which are protected from the bulk by the superconducting energy gap. We realize a magnetic kagome lattice on a superconductor by depositing Fe-porphin-chloride molecules on Pb(111) and using temperature-activated de-chlorination and self-assembly. This allows us to control the formation of smaller kagome precursors and long-range ordered kagome islands. Using scanning tunneling microscopy and spectroscopy at 1.6 K, we identify Yu-Shiba-Rusinov states inside the superconducting energy gap and track their hybridization from the precursors to larger islands, where the kagome lattice induces extended YSR bands. These YSR-derived kagome bands are protected inside the superconducting energy gap, motivating further studies to resolve possible spin-liquid or Kondo-lattice-type behavior.