Charge Sensing of Fractional Quantum Hall States in Monolayer Graphene: Part I

Spatially resolving electrostatic and chemical potential enables the measurement of charge distribution in real space, providing unique insights into electronic properties. Recently, C. L. Chiu et al. [1] developed a novel technique that takes advantage of the high spatial resolution of a scanning tunneling microscope (STM) and transforms it into a chemical potential probe by adding a monolayer graphene detector layer. This architecture provides a less invasive method for probing charge distribution, which was previously inaccessible using conventional STM techniques. In the first talk of a series of two presentations, I will demonstrate how we integrate this charge-sensing technique with our millikelvin STM, allowing measurements at lower temperatures (~200 mK) and higher magnetic fields (9 T). With this approach, we examined the chemical potential evolution of quantum Hall liquids in monolayer graphene across partially filled Landau levels and locally characterized the thermodynamic gaps associated with fractional quantum hall states. Additionally, we mapped the system's electrostatic potential in real space, focusing on its response to charged impurities.

[1] Cheng-Li Chiu et al., High spatial resolution charge sensing of quantum Hall states. Preprint at https://doi.org/10.48550/arXiv.2410.10961 (2024).