Magnetic field effects on a multi-orbital Peierls-Hubbard model: implications for vanadium dioxide

We investigate magnetic field effects on a one-dimensional multi-orbital Hubbard model coupled to lattice distortion to clarify the magnetic-field-induced metal-insulator transition observed in VO2. By adopting the Hartree-Fock approximation, we obtain the ground-state phase diagram on the plane of the Hund coupling and the magnetic field, and find that the magnetic field destabilizes the dimerized insulating phase, leading to a forced ferromagnetic metallic phase. Moreover, we demonstrate that the critical field decreases with increasing Hund coupling, suggesting the importance of multi-orbital nature on the metal-insulator transition under magnetic fields.