Localizing Individual Exciton on a Quantum Hall Antidot

Quantum Hall systems host quasiparticles demonstrating correlated electron physics and non-trivial quantum statistics. Excitonic phases, archetypical for interaction effect, have attracted significant interest in recent years in double-layer quantum Hall systems where spatially separated electrons and holes form bosonic condensate through Coulomb interaction. Here, employing the approach of quantum Hall antidot with two spatially separated edge channels, we demonstrate a new type of quantum Hall quasiparticle exciton which represents a quantum-coherent bound state of an electron and a hole situated on their corresponding edges coupled through intralayer tunneling and Coulomb interaction. Quantum-coherent dynamics of the exciton is reflected in the observed evolution of the position and magnitude of the antidot conductance peaks around the electron-hole resonance. The quantum Hall antidot setup allows localization and electrical tuning of individual quantum Hall excitons. Quantum superposition of vacuum- and electron-hole pairing states is observed through the gate-dependent tunneling conductance of the antidot. Modeling the electron-hole pair as a coupled two-level system, semi-quantitative understanding of experimental observations is achieved. This work opens avenues for creating quantum systems of multiple quantum Hall quasiparticles.