Experimental realization of a Fabry-Perot-type interferometer by co-propagating edge states in the integer and fractional quantum Hall effect regimes

A Fabry-Perot-type interferometer is experimentally realized for electrons in a semiconductor device. Interference conditions are created for co-propagating electrons in quantum Hall edge states, which results in oscillations of the current through the device for integer and fractional filling factors. We find the interference oscillations in transport across the incompressible strips with local filling factors íc = 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 íc = 1/3 incompressible strip. This indicates, that even at fractional íc, 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.