Semiconductor-superconductor transition and magnetoresistance terraces in an ultrathin superconducting Pb nanobridge

Using focused ion beam etching technique, the authors fabricated a 28 atomic monolayers thick, 500 nm wide, and $10μm$ long Pb nanobridge from an atomically flat Pb thin film grown on Si by molecular beam epitaxy. Electric transport measurements show exotic resistance oscillations in the superconducting state far below its critical field $HC$ and cascading terraces near the superconducting transition region. Furthermore, the bridge shows an unusual semiconducting behavior above the superconducting transition temperature $TC$⁠. The results are in contrast to those observed in its counterpart of the two-dimensional thin film.