PTCDA Molecular Monolayer on Pb Thin Films: An Unusual <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>π</mml:mi></mml:math>-Electron Kondo System and Its Interplay with a Quantum-Confined Superconductor
Shuangzan Lu, Hyoungdo Nam, Penghao Xiao, Mengke Liu, Yanping Guo, Yusong Bai, Zhengbo Cheng, Jinghao Deng, Yanxing Li, Haitao Zhou, Graeme Henkelman, Gregory A. Fiete, Hong-Jun Gao, Allan H. MacDonald, Chendong Zhang, Chih-Kang Shih
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 ultrathin 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 π electron impurity lattice on a superconductor in the regime of T_{K}≫Δ, suggesting the formation of a two-dimensional bound states band. Moreover, moiré superlattices with tunable twist angle and the quantum confinement in the ultrathin 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.