Phase Conjugated Andreev Backscattering in Two-Dimensional Ballistic Cavities

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