Quantum Monte Carlo study of artificial triangular graphene quantum dots

Abstract: We investigate the magnetic phases of triangular graphene quantum dots (TGQDs) with zigzag edges using variational and quantum Monte Carlo methods. These systems serve as quantum simulators for bipartite lattices with broken sublattice symmetry, providing a platform to study the extended Hubbard model's emergent magnetic phenomena, including Lieb's magnetism at half-filling, edge depolarization upon single-electron addition, and Nagaoka ferromagnetism. Our non-perturbative quantum Monte Carlo simulations, performed for lattices of up to 61 sites, reveal that TGQDs transition from metallic to insulating regimes as a function of site radius size, while retaining edge-polarized ground states at half-filling. Notably, edge depolarization occurs upon single-electron doping in both metallic and insulating phases, contrasting with the Nagaoka ferromagnetism observed in hexagonal armchair geometries.