Fractional Super-Periods of the Flux in Anyonic Interference

We present observations of anyonic interference in the FQHE regime, showing non-integer super-periods of the magnetic flux in a novel co-propagating 'optical-like' Mach-Zehnder interferometer. For particle-like fractional fillings in the lowest Landau level, ν=1/3, 2/5, and 3/7, the observed flux periodicities were 3Φ₀, 5Φ₀, and 7Φ₀, corresponding to interfering quasiparticle charges of e^*=e/3, e/5, and e/7. In contrast, for the particle-hole conjugate states ν=2/3, 3/5, and 4/7, which support topological upstream neutral modes, the measured periodicities were 3Φ₀/2, 5Φ₀/3, and 7Φ₀/4. Similarly, the shot noise Fano factors in each QPC of the interferometer match e^* in particle-like states, while for hole-conjugate states, they are instead set by the filling factors. Our measurements suggest that the neutral modes play a central role and carry vital information about the fractional state. The additional noise arising at the QPCs due to these modes interplays with the interfering edge modes, ‘dressing’ the interfering quasiparticles with charge νe.