Electronic correlations and pressure-induced metallicity in LaMnPO1-xFx revealed via infrared spectroscopy

We spectroscopically investigated the energy gap of the correlated antiferromagnetic insulator LaMnPO1-xFx (x = 0.0 and 0.04) as a function of temperature and pressure, separately, in conjunction with many-body electronic structure calculations. These results show that the electronic structure in all measured regimes is well described by a model that includes both Mott-Hubbard interactions and Hund's rule coupling. Moreover, we find that by applying external pressure, thereby reducing the effective Mott-Hubbard interaction and Hund's coupling, the energy gap in LaMnPO1 xFx can be fully closed, yielding a metallic state.