Proximity-Induced\nSuperconductivity in a 2D Kondo\nLattice of an <i>f</i>‑Electron-Based Surface Alloy

Realizing hybrids of low-dimensional Kondo lattices and\nsuperconducting\nsubstrates leads to fascinating platforms for studying the exciting\nphysics of strongly correlated electron systems with induced superconducting\npairing. Here, we report a scanning tunneling microscopy and spectroscopy\nstudy of a new type of two-dimensional (2D) La–Ce alloy grown\nepitaxially on a superconducting Re(0001) substrate. We observe the\ncharacteristic spectroscopic signature of a hybridization gap evidencing\nthe coherent spin screening in the 2D Kondo lattice realized by the\nultrathin La–Ce alloy film on normal conducting Re(0001). Upon\nlowering the temperature below the critical temperature of rhenium,\na superconducting gap is induced exhibiting an energy asymmetry of\nthe coherence peaks that arises from the interaction of residual unscreened\nmagnetic moments with the superconducting substrate. A positive correlation\nbetween the Kondo hybridization gap and the asymmetry of the coherence\npeaks is found.