High-Resolution Tunneling Spectroscopy of Fractional Quantum Hall States

Abstract

Strong interaction between electrons in two-dimensional systems in the presence of a high magnetic field gives rise to fractional quantum Hall states that host quasiparticles with fractional charge and fractional exchange statistics. Here, we demonstrate high-resolution scanning tunneling microscopy and spectroscopy of fractional quantum Hall states in ultra clean Bernal-stacked bilayer graphene devices. Spectroscopy measurements show sharp excitations that have been predicted to emerge when electrons fractionalize into bound states of quasiparticles. We find energy gaps for candidate non-abelian fractional states that are larger by a factor of five than other related systems - for example semiconductor heterostructures - and this suggests bilayer graphene is an ideal platform for the manipulation of these quasiparticles and for the creation of a topological quantum bit. We also find previously unobserved fractional states in our very clean graphene samples.