Scanning tunneling spectroscopy study of proximity superconductivity in finite-size quantized surface states

Normal metals can inherit superconducting pairing when they are proximity-coupled to a superconducting host material. Creating two-dimensional surface states with this pairing can lead to exotic phases of matter. However, their localized nature weakens direct coupling to the host material. This study explores how, despite weak intrinsic coupling -- as evident by the observation of several Machida-Shibata-States in high-resolution tunneling spectroscopy -- the surface states in Ag(111) and Cu(111) still achieve superconductivity through scattering from step edges and defects.