Imaging Electron-Hole Asymmetry in the Quantum Melting of Generalized Wigner Crystals

TL;DR

This study uses STM to visualize how generalized Wigner crystals in twisted MoSe2 exhibit electron-hole asymmetry during melting, revealing different disordered and liquid-like states driven by moiré superlattice symmetry breaking.

Contribution

First direct imaging of electron-hole asymmetric melting of generalized Wigner crystals in moiré materials, linking asymmetry to moiré superlattice properties.

Findings

Hole-doped GWCs become disordered states.

Electron-doped GWCs melt into liquid-like states.

Mott insulators melt symmetrically without asymmetry.

Abstract

Two-dimensional moir\'e materials provide a versatile platform to explore phase transitions in strongly correlated systems. Using scanning tunneling microscopy (STM) we have imaged the density-driven melting of generalized Wigner crystals (GWCs) and Mott insulators (MIs) in electron-doped, near-60{\deg} twisted MoSe2 bilayers featuring a triangular moir\'e superlattice. We observe striking electron-hole asymmetry in GWC melting: hole-doped GWCs yield interaction-driven disordered states whereas electron-doped GWCs melt into delocalized liquid-like states. This asymmetry arises from the broken particle-hole symmetry of the moir\'e superlattice, which produces electron and hole Fermi pockets with different momentum geometries upon GWC condensation. MI states melt without such asymmetry, consistent with the absence of a symmetry-breaking density modulation. This work provides direct visualization of the novel emergent phases that appear as GWCs undergo quantum melting transitions.