Pressure-Driven Metal-Insulator Transition in Hematite from Dynamical Mean-Field Theory

The local density approximation combined with dynamical mean-field theory is applied to study the paramagnetic and magnetically ordered phases of hematite Fe₂O₃ as a function of volume. As the volume is decreased, a simultaneous first-order insulator-metal and high-spin to low-spin transition occurs close to the experimental value of the critical volume. The high-spin insulating phase is destroyed by a progressive reduction of the spectral gap with increasing pressure, upon closing of which the high-spin phase becomes unstable. We conclude that the transition in Fe₂O₃ at ≈50  GPa can be described as an electronically driven volume collapse.