Current–voltage characteristics of asymmetric double-barrier Josephson junctions

• We calculate current voltage characteristics of superconductor-normal metal Josephson junctions with resistive interfaces.
• The theory applies to nanowire Josephson junctions and multilayered metallic Josephson structures.
• We find novel current features at the combination subharmonics of the proximity minigap and the bulk energy gap.

We develop a theory for the current–voltage characteristics of diffusive superconductor-normal metal–superconductor Josephson junctions with resistive interfaces and the distance between the electrodes smaller than the superconducting coherence length. The theory allows for a quantitative analytical and numerical analysis in the whole range of the interface transparencies and asymmetry. We focus on the regime of large interface resistance compared to the resistance of the normal region, when the electron–hole dephasing in the normal region is significant and the finite length of the junction plays a role. In the limit of strong asymmetry we find pronounced current structures at the combination subharmonics of Δ+ΔgΔ+Δg, where ΔgΔg is the proximity minigap in the normal region, in addition to the subharmonics of the energy gap 2Δ2Δ in the electrodes. In the limit of rather transparent interfaces, our theory recovers a known formula for the current in a short mesoscopic connector – a convolution of the current through a single-channel point contact with the transparency distribution for an asymmetric double-barrier potential.