Observation of Superconductor-insulator Transition Induced by Ge in Ultrathin a-Nb Film

摘要

We have observed the superconductor-insulator (S-I) transition induced by over-deposited Ge in the ultrathin amorphous Nb (a-Nb) film. The experiments are performed by depositing Ge onto the insulating a-Nb film with a thickness of 1.04 nm. For d_(Ge) > 0.3 nm, where d_(Ge) was a thickness for Ge film, the reduction of electrical sheet resistances was seen at low temperature region, suggesting superconductor. Moreover, the normal sheet resistance at 8 K decreased monotonously with increasing d_(Ge). The simplest explanation of this S-I transition is that the electron localization effect is weakened due to the addition of Ge film.