Quasiparticle-pair interference effect in proximity-coupled junction ladders

Abstract

We observed the quasiparticle-pair interference effect in arrays of Pb/Cu proximity-coupled junctions using de electrical conduction measurements. The effect caused a maximum in magnetoresistance at temperatures T greater than or equal to 3.70 K for integer values of filling factor f, and a beatlike pattern in the wide-field-range magnetoresistance, which is contrary to the usual behavior of Josephson-junction arrays. Numerical simulation on a single-plaquette array and a small-size ladder indicates that the prefactor of the interference cos phi term close to -1 best explains the results.