Optical readout of the chemical potential of two-dimensional electrons

Abstract

The chemical potential u of an electron system is a fundamental property of a solid. A precise measurement of u plays a crucial role in understanding the electron interaction and quantum states of matter. However, thermodynamics measurements in micro and nanoscale samples are challenging because of the small sample volume and large background signals. Here, we report an optical readout technique for u of an arbitrary two-dimensional (2D) material. A monolayer semiconductor sensor is capacitively coupled to the sample. The sensor optical response determines a bias that fixes its chemical potential to the band edge and directly reads u of the sample. We demonstrate the technique in AB-stacked MoTe2/WSe2 moire bilayers. We obtain u with DC sensitivity about 20 ueV/sqrt(Hz), and the compressibility and interlayer electric polarization using AC readout. The results reveal a correlated insulating state at the doping density of one hole per moire unit cell, which evolves from a Mott to a charge-transfer insulator with increasing out-of-plane electric field. Furthermore, we image u and quantify the spatial inhomogeneity of the sample. Our work opens the door for high spatial and temporal resolution measurements of the thermodynamic properties of 2D quantum materials.

References in corpus (9)

• Quantum anomalous Hall effect from intertwined moiré bands
• Continuous Mott transition in semiconductor moiré superlattices
• Atomically thin mirrors made of monolayer semiconductors
• Realization of an atomically thin mirror using monolayer MoSe2
• Gate-tunable heavy fermions in a moiré Kondo lattice
• Topological Phases in AB-Stacked MoTe${}_2$/WSe${}_2$: ${\mathbb{Z}}_2$ Topological Insulators, Chern Insulators, and Topological Charge Density Waves
• Charge-order-enhanced capacitance in semiconductor moiré superlattices
• Spin-Orbit Coupling in Transition Metal Dichalcogenide Heterobilayer Flat Bands
• Quantum anomalous Hall effect from inverted charge transfer gap

Cited by in corpus (1)

• Quantum control of Hubbard excitons