Superconductivity and quantum oscillations in crystalline Bi nanowires

While bulk bismuth (Bi) is a semimetal, we have found clear evidence of superconductivity in a crystalline 72 nm diameter Bi nanowire below 1.3 K. In a parallel magnetic field (H), the residual resistance of the nanowire below Tc displays periodic oscillations with H, and the period corresponds to the superconducting flux quantum. This result provides evidence that the superconductivity comes from the interface shell between Bi and the surface oxide. In a perpendicular H, the resistance in the superconducting state shows Shubnikov-de Haas (SdH) oscillations, a signature of a normal metal. These results indicate a novel coexistence of Bosonic and Fermionic states in the surface shell of nanowires.