Fabrication of quantum Hall interferometers in high quality graphene van der Waals heterostructures using local oxidation lithography

Fabry-Pérot interferometry of fractional quantum Hall edge states has long been known to provide an effective experimental probe of non-abelian statistics, for instance in even denominator fractional quantum Hall states. Recent work in high quality bilayer graphene van der Waals heterostructures has revealed even-denominator states with large energy gaps, bringing such experiments within reach. However, fabrication of the requisite gate geometries in a van der Waals heterostructure is challenging due to the absence of a band gap and the disorder typically introduced by standard additive as well as subtractive nanofabrication processes. In this talk, we will present progress towards improved gate-defined Fabry-Pérot interferometers using AFM oxidation lithography. We show that sub-100 nm features can be patterned in graphite flakes, and these patterns transferred into arbitrary gate layers within a van der Waals heterostructure. Besides applications in quantum Hall effects, our results suggest a versatile new architecture for local electrostatic control of ultra-high mobility two dimensional electron systems.