THE AHARONOV-CASHER EFFECT FOR VORTICES IN JOSEPHSON-JUNCTION ARRAYS

We report on an experiment where we observe quantum mechanical interfe rence of vortices around an induced charge. In a specially designed sa mple, vortices cross along a doubly connected path. On the superconduc ting island enclosed by the two paths a charge can be induced by capac itive coupling to a gate. In the resistance that arises from the movin g vortices we find clear oscillations as a function of gate voltage. T he period of the oscillation corresponds to the single electron charge e, due to the presence of a finite amount of quasiparticles. The osci llations demonstrate quantum interference of vortices which is a manif estation of the generalized Aharonov-Casher effect.