PTCDA molecular monolayer on Pb thin films: An unusual {\pi}-electron Kondo system and its interplay with a quantum-confined superconductor

TL;DR

This study explores a novel hybrid system where a PTCDA molecular monolayer on ultra-thin Pb films exhibits unique pi-electron Kondo effects and their interaction with quantum-confined superconductivity, revealing new physical phenomena.

Contribution

It introduces a new M/SC hybrid system based on sp-electron molecules and demonstrates tunable interplay between Kondo physics and superconductivity.

Findings

Observation of Kondo screened pi-electron impurity lattice on superconductor

Detection of a two-dimensional bound states band formation

Tunable interplay between Kondo effect and superconductivity via moiré superlattices

Abstract

The hybridization of magnetism and superconductivity has been an intriguing playground for correlated electron systems, hosting various novel physical phenomena. Usually, localized d- or f-electrons are central to magnetism. In this study, by placing a PTCDA (3,4,9,10-perylene tetracarboxylic dianhydride) molecular monolayer on ultra-thin Pb films, we built a hybrid magnetism/superconductivity (M/SC) system consisting of only sp electronic levels. The magnetic moments reside in the unpaired molecular orbital originating from interfacial charge-transfers. We reported distinctive tunneling spectroscopic features of such a Kondo screened pi-electron impurity lattice on a superconductor in the regime of TK>>delta suggesting the formation of a two-dimensional bound states band. Moreover, moir\'e superlattices with tunable twist angle and the quantum confinement in the ultra-thin Pb films provide easy and flexible implementations to tune the interplay between the Kondo physics and the superconductivity, which are rarely present in M/SC hybrid systems.