  In recent interference experiments with an electronic Fabry-Perot
interferometer (FPI), implemented in the integer quantum Hall effect regime, a
flux periodicity of $h/2e$ was observed at bulk fillings $\nu_B>2.5$. The
halved periodicity was accompanied by an interfering charge $e^*=2e$,
determined by shot noise measurements. Here, we present measurements,
demonstrating that, counterintuitively, the coherence and the interference
periodicity of the interfering chiral edge channel are solely determined by the
coherence and the enclosed flux of the adjacent edge channel. Our results
elucidate the important role of the latter and suggest that a neutral chiral
edge mode plays a crucial role in the pairing phenomenon. Our findings reveal
that the observed pairing of electrons is not a curious isolated phenomenon,
but one of many manifestations of unexpected edge physics in the quantum Hall
effect regime.
