Imaging local discharge cascades for correlated electrons in WS2/WSe2 moir�� superlattices

Transition metal dichalcogenide (TMD) moir�� 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�� superlattice that enables experimental extraction of fundamental extended Hubbard model parameters. We demonstrate that the charge state of local moir�� 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�� 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�� electron charge states also enables us to determine onsite energy fluctuations at different moir�� sites. Our technique should be broadly applicable to many semiconductor moir�� systems, offering a powerful new tool for microscopic characterization and control of strongly correlated states in moir�� superlattices.