Pressure induced metallic state in LaMnPO revealed via Infrared spectroscopy

We investigated the energy gap (E$_{Gap}$) of the antiferromagnetic insulator LaMnPO$_{1-x}$F$_{x}$ for x = 0.0, 0.04, as a function of temperature and pressure using infrared spectroscopy. The results obtained from these measurements show that the band gap shows no discontinuous change upon crossing the Ne\'el temperature of 375 K and is therefore, likely unrelated to the antiferromagnetic ordering. Despite the resilience of the band gap to temperature, the band gap is dramatically reduced with the application of pressure and fully collapses by 28 GPa for both samples. These measurements confirm theoretical work predicting the collapse of the band gap with pressure.