Coupled Yu-Shiba-Rusinov states induced by a many-body molecular spin on a superconductor

TL;DR

This study demonstrates that intramolecular exchange interactions in a magnetic molecule on a superconductor can produce coupled Yu-Shiba-Rusinov states, enabling new entangled superconducting bound states with potential for quantum engineering.

Contribution

It reveals that molecular exchange interactions can induce coupled YSR states across a molecule, a novel mechanism for engineering entangled superconducting states.

Findings

Evidence of two orbital interaction channels with inverted particle-hole asymmetry.

Numerical confirmation of coupled YSR states caused by opposite potential scattering.

Potential for tunneling excitation of entangled bound states in molecular platforms.

Abstract

A magnetic impurity on a superconductor induces Yu-Shiba-Rusinov (YSR) bound states, detected by tunneling spectroscopy as long-lived quasiparticle excitations inside the superconducting gap. Coupled YSR states constitute basic elements to engineer artificial superconducting states, but their substrate-mediated interactions are generally weak. In this paper, we report that intramolecular (Hund's like) exchange interactions produce coupled YSR states across a molecular platform. We measured YSR spectra along a magnetic iron-porphyrin on Pb(111) and found evidences of two orbital interaction channels, which invert their particle-hole asymmetry across the molecule. Numerical calculations show that the identical YSR asymmetry pattern of the two channels is caused by two spin-hosting orbitals with opposite potential scattering and coupled strongly. Both channels can be similarly excited by tunneling electrons into each orbital, depicting a new scenario for entangled superconducting bound states using molecular platforms.