Ballistic Josephson-current flow through an asymmetric superconductor–normal-metal–superconductor junction

Li-Fu Chang; Philip F. Bagwell

doi:10.1103/PhysRevB.49.15853

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Ballistic Josephson-current flow through an asymmetric superconductor–normal-metal–superconductor junction

Li-Fu Chang, Philip F. Bagwell

DOI 10.1103/PhysRevB.49.15853 · Physical Review B

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Abstract

We study the Josephson current through a ballistic, normal metal, mesoscopic, one-dimensional quantum channel in contact with two superconducting electrodes. The two superconductors have different energy gaps Δ1 and Δ2. Increasing either energy gap increases the critical current Ic. This enhancement of Ic results from altering the mesoscopic processes which control the Josephson-current flow, rather than through the proximity effect. The effect is strongest in junctions shorter than the size of a Cooper pair. When the asymmetry is large, such that Δ2≫Δ1, we find the critical current can be several times larger than its bulk value in the weaker superconductor, namely, Ic>eΔ1/ħ.