ac Josephson effect for asymmetric superconducting junctions

Magnus Hurd; Supriyo Datta; Philip F. Bagwell

doi:10.1103/PhysRevB.56.11232

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ac Josephson effect for asymmetric superconducting junctions

Magnus Hurd, Supriyo Datta, Philip F. Bagwell

DOI 10.1103/PhysRevB.56.11232 · Physical Review B

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Abstract

We calculate the ac and dc current-voltage (I−V) relation when a tunnel barrier is placed in the normal region of a superconductor–normal-metal–superconductor (S1NS2) junction, where the two superconducting contacts have different gaps (Δ2>~Δ1>~0). The voltages at which subharmonic gap structure (SGS) appears in the zero-temperature I−V are the same as previously found for the SGS in ballistic S1NS2 junctions at a finite temperature. Some of the SGS’s are strong enough to produce negative differential resistance. We determine the variation of the ac Josephson current with bias, junction transmissivity, gap ratio Δ1/Δ2, and junction length L. The ac Josephson current through a ballistic SNS junction can also be used to measure the superconducting phase difference φ.