Imaging electron-hole asymmetry in the quantum melting of generalized Wigner crystals

Two-dimensional moiré materials provide a versatile platform to explore phase transitions in strongly correlated systems. Using scanning tunneling microscopy, we imaged the density-driven melting of generalized Wigner crystals (GWCs) and Mott insulators (MIs) in electron-doped, near-60°–twisted molybdenum diselenide bilayers featuring a triangular moiré superlattice. We observed notable electron-hole asymmetry in GWC melting: Hole-doped GWCs yielded interaction-driven disordered states, whereas electron-doped GWCs melted into delocalized liquid-like states. This asymmetry arose from the broken particle-hole symmetry of the moiré superlattice, which produced electron and hole Fermi pockets with different momentum geometries upon GWC condensation. MI states melted without such asymmetry, consistent with the absence of a symmetry-breaking density modulation. This work provides direct visualization of the emergent phases that appear as GWCs undergo quantum melting transitions.