Imaging Disordered Electronic Phases and Quantum Melting in Generalized Wigner Crystals

Moiré superlattices fabricated from two-dimensional materials offer a versatile platform to explore unconventional correlated electron phases by tuning parameters such as interaction strength and carrier density. We have used scanning tunneling microscopy (STM) to directly image the density-tuned melting of generalized Wigner crystals (GWCs) and Mott insulators (MI) in an electron-doped twisted MoSe₂ moiré bilayer stacked near 60°. We see striking electron–hole asymmetry in density-tuned GWC melting at slight departures from commensurate fillings. Removing electrons from GWCs yields a novel 2D disordered phase – an interaction-driven amorphous state with local charge fluctuations arising from frustrated charge order.  Adding electrons yields a uniform, delocalized phase, consistent with Fermi liquid behavior. This electron-hole asymmetry reflects the broken particle-hole symmetry of triangular lattices which results in the formation of dissimilar doping-induced Fermi pockets for electrons and holes upon GWC condensation. Such asymmetry is absent for the MI state, consistent with the absence of a symmetry breaking density modulation.