Quantum Hall antidot as a fractional coulombmeter
Nature Physics Springer Nature
Authors:
Mario Di Luca, Emily Hajigeorgiou, Zekang Zhou, Tevz Lotric, Tengyan Fang, Kenji Watanabe, Takashi Taniguchi, Steven Simon, Mitali Banerjee
Abstract:
The ability to detect fractionally charged quasiparticles, which arise in the fractional quantum Hall regime, is of fundamental importance for probing their exotic quantum properties. While electronic interferometers have been central to probe their statistical properties, their interpretation is often complicated by bulk–edge interactions. Antidots, potential hills in the quantum Hall regime, are particularly valuable in this context, as they overcome the geometric limitations of conventional designs and act as controlled impurities within a quantum point contact. In this work, we employ a gate-defined bilayer graphene antidot operating in the Coulomb-dominated regime to study quasiparticle tunneling in both integer and fractional quantum Hall states. We show that the gate-voltage period and the oscillation slope directly reveal the charge of tunneling quasiparticles. We report direct measurements of fractional charge, finding q = e/3 at ν = 4/3, 5/3 and 7/3, q = 2e/3 at ν = 2/3 and q = 3e/5 at ν = 3/5, while at ν = 8/3 we observe signatures of both e/3 and 2e/3 tunneling charge. We derive a theoretical model that indicates that the differences in the measured charges may be attributed to variations in edge re-equilibration arising from a different parity of downstream integer edge modes. The simplicity and tunability of this design open a pathway to extend antidot-based charge measurements to other van der Waals materials, establishing antidots as a broadly applicable platform to study topological materials.
