Dissipative charge transport in diffusive superconducting double-barrier junctions

TL;DR

This paper analyzes charge transport in diffusive superconducting junctions, revealing how phase shifts influence current-voltage characteristics and identifying regimes with negative differential resistance.

Contribution

It provides a theoretical solution for MAR in SINIS junctions considering phase dephasing, extending known formulas to new regimes and highlighting the role of dephasing as an effective tunneling parameter.

Findings

At low dephasing, the model recovers known MAR formulas.

At high dephasing, subharmonic gap structures scale with 1/γ.

Negative differential resistance appears at large dephasing.

Abstract

We solve the coherent multiple Andreev reflection (MAR) problem and calculate current-voltage characteristics (IVCs) for Josephson SINIS junctions, where S are local-equilibrium superconducting reservoirs, I denotes tunnel barriers, and N is a short diffusive normal wire, the length of which is much smaller than the coherence length, and the resistance is much smaller than the resistance of the tunnel barriers. The charge transport regime in such junctions qualitatively depends on a characteristic value \gamma = \Delta \tau_d of relative phase shifts between the electrons and retro-reflected holes accumulated during the dwell time \tau_d. In the limit of small electron-hole dephasing \gamma << 1, our solution recovers a known formula for a short mesoscopic connector extended to the MAR regime. At large dephasing, the subharmonic gap structure in the IVC scales with 1/ \gamma, which thus plays the role of an effective tunneling parameter. In this limit, the even gap subharmonics are resonantly enhanced, and the IVC exhibits portions with negative differential resistance.