A Scalable Platform of Deterministic Flat Band : Epitaxial Monolayer WS2 on Au (111) via Lattice Mismatch-driven Colossal Moiré Potential

Flat bands in two-dimensional materials offer a promising route to correlated electronic phases, but their realization typically requires fine twist angle control. Here, we present a scalable platform for deterministic flat band engineering, realized in an epitaxial monolayer of WS₂ on a Au (111) substrate. The flat band is driven by a colossal Moiré potential, originating from the intrinsic lattice mismatch. This mechanism, based on strong potential energy confinement, is fundamentally distinct from the kinetic energy quenching in twisted systems. By combining scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS), we directly visualize the resulting spatially confined, non-dispersive electronic states. Crucially, through work-function mapping, we directly visualize and quantify this colossal potential landscape, revealing a periodic modulation of ~350 meV that spatially localizes the electronic states. First-principles calculations confirm that the observed spatial potential landscape originates from strong substrate-induced electronic hybridization. Our work establishes that lattice mismatch-driven Moiré potential provides a deterministic and scalable route to flat bands, offering a new platform for exploring correlated quantum phenomena and applications.