Correlated Electron Effects in Chromium Trihalide Hetostructures with Graphene: A Tight-Binding Model Perspective

In this study, we present an effective tight-binding model for an accurate description of the lowest energy quadruplet of conduction band in a ferromagnetic CrX₃ monolayer, tuned to the complementary ab initio density functional theory simulations. This model, based on a minimum number of chromium orbitals, captures a distinctively flat dispersion in those bands but requires taking into account hoppings beyond nearest neighbours, revealing ligand-mediated electron pathways connecting remote chromium sites. Doping of states in the lowest conduction band of CrX₃ requires charge transfer, which, according to recent studies, can occur in graphene(G)/CrX₃ heterostructures. Here, we use the detailed description of the lowest conduction band in CrI₃ to show that G/CrI₃/G and G/CrI₃ are type-II heterostructures where light holes in graphene would coexist with heavy electrons in the magnetic layer, where the latter can be characterised by Wigner parameter rₛ~ 15-20 (as estimated for hBN-encapsulated structures).