  We study the Mott metal-insulator transition in the Hubbard-Hofstadter model
as a function of the orbital magnetic field, exploiting dynamical mean field
theory (DMFT). Considering interaction strengths between the electrons for
which this model is in the Mott insulating state in the field-free case, we
find that for sufficiently large magnetic fields a metallic phase emerges. Upon
decreasing the field, we observe a metal-insulator transition from this
metallic to an insulating state. This effect can be understood by a magnetic
field induced increase of the kinetic energy due to the formation of magnetic
mini-bands which enhances the ratio between the kinetic and potential energy
and can, thus, trigger a transition between a metallic and insulating phase.
Our findings are in good qualitative agreement with a recent experiment [Nature
Communications 11, 3591] on vanadium oxide (VO$_2$) where a magnetic field
driven insulator-to-metal transition has been observed at strong magnetic
fields.
