Low Temperature Scanning Tunneling Microscopy on Nano-size Superconductors

Abstract

Using low-temperature scanning tunneling microscopy, we have studied superconductivity of nano-size Pb island structures formed on Si(111) substrates. By measuring tunneling conductance at the zero bias voltage, which corresponds to that of the bottom of the superconducting gap, we successfully visualized vortices formed in the superconductors and studied their spatial distributions. Clustering of vortices and a giant vortex structure were observed on islands having void structures.