  Interference of edge channels is expected to be a prominent tool for studying
statistics of charged quasiparticles in the quantum Hall effect (QHE) [A. Stern
(2008), Ann. Phys. 1:204; C. Chamon et al. (1997), Phys. Rev. B, 55:2331]. We
present here a detailed study of an electronic Fabry-Perot interferometer (FPI)
operating in the QHE regime [C. Chamon et al. (1997), Phys. Rev. B, 55:2331],
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. In particular, for a composite edge structure, with a few
independent edge channels propagating along the edge, interference of the
outmost edge channel (belonging to the lowest Landau level) was insensitive to
magnetic field; suggesting a constant enclosed flux. However, when any of the
inner edge channels interfered, the enclosed flux decreased when the magnetic
field increased. 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 found to be expelled from the FPI. Moreover, these observations
provided also a novel way of detecting the charge of the interfering
quasiparticles.
