Optically Probed Correlated Electrons in a Purely Electrostatic Moiré Potential

Moiré heterostructures based on transition metal dichalcogenide (TMD) hetero- and homobilayers have recently become a key material platform for exploring correlated electronic states. The use of a moiré substrate with a twisted hexagonal boron nitride (h-BN) interface constitutes a new, flexible way to externally generate a periodic superlattice for any van der Waals target material. In this work, we place a MoSe2 monolayer directly next to a twisted h-BN bilayer in a dual-gated, charge and electric field tunable device. The periodic arrangement of ferroelectric domains in twisted h-BN creates a purely electrostatic potential for charge carriers in the MoSe2 layer. The charge-neutral TMD exciton, which is to first order not affected by the potential, serves as a spin-valley-sensitive probe of the electron state. We report the emergence of new excitonic resonances at integer fillings and an enhancement of the trion binding energy due to the localization of electrons. Furthermore, we find direct evidence of charge order associated with electronic Mott–Wigner states at filling factors ν = 1/3 and ν = 2/3, revealed through exciton Umklapp resonances.