Optical sensing of fractional quantum Hall effect in graphene

TL;DR

This paper introduces a novel all-optical spectroscopic method using Rydberg excitons in TMD monolayers to detect fractional quantum Hall states in graphene, enabling non-invasive, high-resolution studies of electronic correlations.

Contribution

It presents a new optical technique to probe fractional quantum Hall states in graphene, overcoming limitations of traditional transport methods.

Findings

Detected odd-denominator FQH states at high magnetic fields

Demonstrated sub-micron spatial resolution in optical detection

Enabled non-invasive probing of correlated electronic states

Abstract

Graphene and its van der Waals (vdW) heterostructures provide a unique and versatile playground for explorations of strongly correlated electronic phases, ranging from unconventional fractional quantum Hall (FQH) states in a monolayer system to a plethora of superconducting and insulating states in twisted bilayers. However, the access to those fascinating phases has been thus far entirely restricted to transport techniques, due to the lack of a robust energy bandgap that makes graphene hard to access optically. Here we demonstrate an all-optical, non-invasive spectroscopic tool for probing electronic correlations in graphene using excited Rydberg excitons in an adjacent transition metal dichalcogenide monolayer. Due to their large Bohr radii, Rydberg states are highly susceptible to the compressibility of graphene electrons, allowing us to detect the formation of odd-denominator FQH states at high magnetic fields. Owing to its sub-micron spatial resolution, the technique we demonstrate circumvents spatial inhomogeneities in vdW structures, and paves the way for optical studies of correlated states in twisted bilayer graphene and other optically inactive atomically-thin materials.