Coherent electronic backscattering in ballistic microstructures

A magnetoresistance peak at zero magnetic field due to coherent backscattering is studied in submicrometer quantum dots with quantum-point-contact leads. A systematic series of experiments on ballistic microstructures shows that coherent backscattering is distinct from conductance fluctuations at finite fields and gives properties in agreement with semiclassical theory. The effect results from interference between pairs of time-reversed paths of ballistic electrons scattered from the walls of the dot, analogous to weak localization in diffusive systems.