Suppression of Mott-Hubbard states and metal-insulator transitions in the two-band Hubbard model

摘要

I investigate band and Mott insulating states in a two-band Hubbard model, with the aim of understanding the differences,between the idealized one-orbital model and the more realistic multi-band case. Using a projection ansatz I show that. additional orbitals suppress the metal-insulator transition, leading to a critical coupling of approximately eight times the bare bandwidth. I also demonstrate the effects of orbital ordering, which hinder Mott-Hubbard states and open a bandgap. Since multi-band correlations are common in real materials, this work suggests that very strongly correlated band insulators may be more common than Mott-Hubbard insulators.