Squeezed Abrikosov-Josephson Vortex in Atomic-Layer Pb Superconductors Formed on Vicinal Si(111) Substrates

Unlike bulk counterparts, two-dimensional (2D) superconductors are sensitive to disorder. Here, we investigated superconductivity of Pb atomic layers formed on vicinal substrates to reveal how surface steps with an interval shorter than the coherence length xi affect it. Electrical transport showed reduced critical temperature and enhanced critical magnetic field. Scanning tunneling microscopy exhibited vortices elongated along the steps, that is, Abrikosov-Josephson vortices squeezed normal to the steps due to the reduced xi. These results demonstrate that steps work as disorder and vicinal substrates provide a unique platform to manipulate the degree of disorder on 2D superconductors.

Automated summary

Unlike bulk superconductors, the superconductivity of Pb atomic layers on vicinal substrates is affected by surface steps. The critical temperature is reduced and the critical magnetic field is enhanced. Scanning tunneling microscopy reveals elongated vortices along the steps due to the reduced coherence length, which demonstrates that the steps act as disorder. Vicinal substrates provide a unique platform to manipulate the degree of disorder on 2D superconductors.