Implementation and Characterization of the Dice Lattice in the Electron Quantum Simulator

Materials featuring touching points, localized states, and flat bands are of great interest in condensed matter and artificial systems due to their implications in topology, quantum geometry, superconductivity, and interactions. In this theoretical study, the experimental realization of the dice lattice with adjustable parameters is proposed by arranging carbon monoxide molecules on a two-dimensional (2D) electron system at a (111) copper surface. First, a theoretical framework is developed to obtain the spectral properties within a nearly free electron approximation and then compare them with tight-binding calculations. This investigation reveals that the high mobility of Shockley state electrons enables an accurate theoretical description of the artificial lattice using a next-nearest-neighbor tight-binding model, resulting in the emergence of a touching point, a quasi-flat band, and localized lattice site behavior in the local density of states. Additionally, theoretical results for a long-wavelength low-energy model that accounts for next-nearest-neighbor hopping terms are presented. Furthermore, the model's behavior under an external magnetic field is theoretically examined by employing Peierl's substitution, a commonly used technique in theoretical physics to incorporate magnetic fields into lattice models. The theoretical findings suggest that, owing to the exceptional electron mobility, the highly degenerate eigenenergy associated with the Aharonov-Bohm caging mechanism may not manifest in the proposed experiment.