Proximity Effect and Multiple Andreev Reflections in Chaotic Josephson junctions

Abstract

We study the dc-current transport in a voltage biased superconductor-chaotic dot-superconductor junction with an induced proximity effect(PE) in the dot. It is found that for a Thouless energy $E_{Th}$ of the dot smaller than the superconducting energy gap $\Delta$, the PE is manifested as peaks in the differential conductance at voltages of order $E_{Th}$ away from the even subharmonic gap structures $eV \approx 2(\Delta\pm E_{Th})/2n$. These peaks are insensitive to temperatures $kT \ll \Delta$ but are suppressed by a weak magnetic field. The current for suppressed PE is independent of $E_{Th}$ and magnetic field and is shown to be given by the Octavio-Tinkham-Blonder-Klapwijk theory.