PHASE CONJUGATED ANDREEV BACKSCATTERING IN 2-DIMENSIONAL BALLISTIC CAVITIES

We have experimentally investigated transport in two-dimensional balli stic cavities connected to a point contact and to two superconducting electrodes with a tunable macroscopic phase difference. The point cont act resistance oscillates as a function of the phase difference in a w ay which reflects the ballistic nature of the transport in the cavity. We interpret our results in terms of a semiclassical model that relie s on the properties of the phase conjugated trajectories on which a ho le traces the path of the electron back to the emitting point contact. This model provides quantitative predictions (with no fitting paramet ers) as well as a clear physical picture.