Imaging local discharge cascades for correlated electrons in WS2/WSe2 moir\'e superlattices

TL;DR

This paper introduces a novel STM technique to image and manipulate correlated electrons in WS2/WSe2 moiré superlattices, enabling direct measurement of extended Hubbard model parameters and advancing understanding of quantum phases.

Contribution

The study develops a new STM-based method for local sensing and control of correlated electrons in moiré superlattices, allowing extraction of fundamental Hubbard model parameters.

Findings

Charge states of moiré sites can be imaged via STM tunneling current.

Discharge cascades can be locally induced by ramping STM bias.

Nearest-neighbor Coulomb interaction (UNN) can be estimated from charge cascades.

Abstract

Transition metal dichalcogenide (TMD) moir\'e heterostructures provide an ideal platform to explore the extended Hubbard model1 where long-range Coulomb interactions play a critical role in determining strongly correlated electron states. This has led to experimental observations of Mott insulator states at half filling2-4 as well as a variety of extended Wigner crystal states at different fractional fillings5-9. Microscopic understanding of these emerging quantum phases, however, is still lacking. Here we describe a novel scanning tunneling microscopy (STM) technique for local sensing and manipulation of correlated electrons in a gated WS2/WSe2 moir\'e superlattice that enables experimental extraction of fundamental extended Hubbard model parameters. We demonstrate that the charge state of local moir\'e sites can be imaged by their influence on STM tunneling current, analogous to the charge-sensing mechanism in a single-electron transistor. In addition to imaging, we are also able to manipulate the charge state of correlated electrons. Discharge cascades of correlated electrons in the moir\'e superlattice are locally induced by ramping the STM bias, thus enabling the nearest-neighbor Coulomb interaction (UNN) to be estimated. 2D mapping of the moir\'e electron charge states also enables us to determine onsite energy fluctuations at different moir\'e sites. Our technique should be broadly applicable to many semiconductor moir\'e systems, offering a powerful new tool for microscopic characterization and control of strongly correlated states in moir\'e superlattices.