Edge-State Velocity and Coherence in a Quantum Hall Fabry-Perot Interferometer

We present finite-bias measurements of electronic Fabry-Perot interferometers in the integer quantum Hall regime. In devices large enough that Coulomb blockade is absent, checkerboard-like patterns of oscillations as a function of magnetic field and dc bias appear. Comparing our data to predictions for electromagnetic Aharonov-Bohm interference, we extract edge-state velocities over a range of magnetic fields, finding dependence consistent with a crossover from skipping orbits at low fields to $E\times B$ drift at high fields. Suppression of visibility observed at high bias and high field is quantitatively accounted for by including an energy-dependent dephasing rate.