Coherent Bunching of Anyons and their Dissociation in Interference Experiments

Abstract

Aharonov-Bohm (AB) interference of fractional quasiparticles in the quantum Hall Effect generally reveals their elementary charge ($e^*$)[1-15]. Recently, our interferometry experiments with several particle states reported flux periods of ${\Delta}{\Phi}=(e/e^*){\Phi}_0$ the flux quantum) at moderate temperatures[16]. Here, we report interference measurements of particle-hole conjugated states at filling factor ${\nu}=2/3, 3/5, 4/7$, revealing unexpected flux periodicities of ${\Delta}{\Phi}={\Phi}_0/{\nu}$. The measured shot noise Fano factor (F) of the partitioned quasiparticles in each of the interferometers quantum point contacts (QPCs), was found to be, $F={\nu}$[17], and not that of the elementary charge, $F=e^*/e$[18,19]. These observations point to interference of bunched (clustered) elementary quasiparticles as coherent pairs, triples, and quadruplets, respectively. A small metallic gate (top gate, TG), deposited in the center of the interferometer bulk, forming an antidot (or a dot) when charged, thus introducing local quasiparticles at the (anti)dots perimeter. Surprisingly, such charging led to a dissociation of the bunched quasiparticles and thus recovered the conventional flux periodicity set by the elementary quasiparticles charge. However, the shot noise Fano factor (of each QPC) consistently remained at $F={\nu}$, possibly due to the neutral modes accompanied the conjugated states. The two observations - bunching and debunching (or dissociation) - are not expected by current theories. Similar effects may likely arise in Jains particle states (at lower temperatures) and at even denominator FQH states[20]