Measurements of Correlated Insulator Gaps in a Transition Metal Dichalcogenide Moir\'e Superlattice

TL;DR

This study directly measures the energy gaps of correlated insulating states in a WS2/WSe2 moiré bilayer using microwave impedance microscopy, revealing their doping dependence and insensitivity to external electric fields, advancing understanding of electron interactions in moiré superlattices.

Contribution

First direct measurement of thermodynamic gaps in WS2/WSe2 moiré bilayers using microwave impedance microscopy, providing new insights into correlated insulators.

Findings

Gaps are relatively insensitive to external electric fields.

Doping dependence of the chemical potential and gaps was characterized.

Microwave impedance microscopy effectively probes correlated insulating states.

Abstract

Moir\'e superlattices of transitional metal dichalcogenides exhibit strong electron-electron interaction that has led to experimental observations of Mott insulators and generalized Wigner crystals. In this letter, we report direct measurements of the thermodynamic gaps of these correlated insulating states in a dual-gate WS2/WSe2 moir\'e bilayer. We employ the microwave impedance microscopy to probe the electronic features in both the graphene top gate and the moir\'e bilayer, from which we extract the doping dependence of the chemical potential of the moir\'e bilayer and the energy gaps for various correlated insulating states utilizing the Landau quantization of graphene. These gaps are relatively insensitive to the application of an external electric field to the WS2/WSe2 moir\'e bilayer.