Observation of enhanced superconductivity in the vicinity of Ar-induced nano-cavities in Pb(111)

Local variations of superconductivity have been studied using scanning tunneling microscopy around nano-cavities formed by Ar ions embedded in Pb(111). Various factors including the density of states at Fermi energy, electron–phonon couplings, and quantum well states, which are known to affect superconductivity, have been examined. We show that the superconductivity is enhanced near the nano-cavities and propose that quantum effects such as quantum confinement, proximity effect and multi-gap effect are possibly involved in determining the superconducting gap of this system. These results have important implications for the characterization and understanding of superconductivity at a nanometer scale.