Interference effects in transport across a single incompressible strip at the edge of the fractional quantum Hall system

We experimentally investigate interference effects in transport across a single incompressible strip at the edge of the quantum Hall system by using a Fabry-Perot type interferometer. We find the interference oscillations in transport across the incompressible strips with local filling factors nu(c)=1,4/3,2/3 even at high imbalances, exceeding the spectral gaps. In contrast, there is no sign of the interference in transport across the principal Laughlin nu(c)=1/3 incompressible strip. This indicates, that even at fractional nu(c), the interference effects are caused by "normal" electrons. The oscillation's period is determined by the effective interferometer area, which is sensitive to the filling factors because of screening effects.