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2005 Nuggets

Research Nugget: Anti-proximity Effect in Superconductor/Zinc Nanowires/ Superconductor Structure
Mingliang Tian, Nitesh Kumar, Shengyong Xu, Jinguo Wang, James S. Kurtz, and M. H. W. Chan, IRG 3

Electrical current flows in a superconductor (S) without resistance and without any loss in energy. When a normal metal (N) is placed in contact with a superconductor, the normal metal acquires superconducting properties due to the leakage of superconducting electrons into the N. This proximity effect was expected not only in planar SN junctions but also in metallic strips between two superconductors. Related behavior is also found in a constriction system consisting of a narrow strip of a superconductor, bridging two bulk superconducting electrodes of the same material. However, we observed a novel and unexpected antiproximity effect in a BS/ZNW/BS system comprising of superconducting zinc nanowires (ZNW) sandwiched between two bulk superconductors (BS), as shown in Figure 1. We found that the superconductivity of ZNW of 40 nm in diameter is suppressed either completely or partially when BS are in the superconducting state. When BS are driven into its normal state by a magnetic field, the nanowires switch back to their superconducting state. This phenomenon is significantly weakened when one of the two BS is replaced by a normal metal. The phenomenon is not seen in wires with diameters equal to and thicker than 70 nm.