The Role of Interactions in an Electronic Fabry-Perot Interferometer Operating in the Quantum Hall Effect Regime

Interference of edge channels is expected to be a prominent tool for studying statistics of charged quasiparticles in the quantum Hall effect (QHE). We present here a detailed study of an electronic Fabry-Perot interferometer (FPI) operating in the QHE regime, with the phase of the interfering quasiparticles controlled by the Aharonov-Bohm (AB) effect. Our main finding is that Coulomb interactions among the electrons dominate the interference, even in a relatively large area FPI, leading to a strong dependence of the area enclosed by the interference loop on the magnetic field. Specifically, for a composite edge structure, with several independent edge channels propagating along the edge, interference of the outermost edge channel was found to be insensitive to magnetic field, suggesting a constant enclosed flux. However, the enclosed flux decreased with increasing magnetic field when any of the inner edge channels interfered. By intentionally varying the enclosed area with a biased metallic gate and observing the periodicity of the interference pattern, charges e (for integer filling factors) and e/3 (for a fractional filling factor) were expelled from the FPI. These observations also provided a novel way of detecting the charge of the interfering quasiparticles.