Coherent Bunching of Anyons and their Dissociation in Interference Experiments

TL;DR

This paper investigates fractional quasiparticle interference in quantum Hall states, revealing unexpected bunching and dissociation phenomena that challenge current theories and suggest complex quasiparticle clustering behavior.

Contribution

It reports novel interference patterns and shot noise results indicating quasiparticle bunching and dissociation in fractional quantum Hall states, not explained by existing models.

Findings

Flux periodicity of Φ₀/ν observed in interference.

Shot noise Fano factor F equals ν, indicating quasiparticle bunching.

Charging antidots leads to quasiparticle dissociation and conventional flux periodicity.

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]