Direct Imaging of Reentrant Wigner Crystallization under Gate-Screened Coulomb Interaction

The interplay between Coulomb interaction and kinetic energy gives rise to a rich phase diagram in two-dimensional electron systems. Analogous to an ionic crystal or solid lattice, a Wigner crystal is a self-organized lattice of electrons (or other charged particles) that forms when Coulomb repulsion dominates over kinetic energy. Recently, stable Wigner crystals have been realized in electrostatically doped two-dimensional semiconductor heterostructures, where they gradually melt into a Fermi liquid as carrier density increases. Here, we report a distinct evolution of correlated electronic states in the presence of a nearby metallic gate that screens the long-range Coulomb interaction, directly visualized by scanning tunneling microscopy. In contrast to the conventional scenario, where a crystalline phase transitions monotonically into a Fermi liquid with increasing density, a strongly screened two-dimensional electron system exhibits liquid-like behavior at low doping. Upon further doping, a Wigner crystal reemerges before undergoing quantum melting back into a liquid phase. These findings demonstrate how reshaping the interaction potential can transform the collective ground state of matter, and point toward a broader framework for engineering correlated quantum phases through controlled interactions.