High-pressure electrical conductivity experiments have been performed on the Mott insulator $\mathrm{MnO}$ to a maximum pressure of $106\mathrm{GPa}$. We observe a steady decrease in resistivity to $90\mathrm{GPa}$, followed by a large, rapid decrease by a factor of ${10}^5$ between 90 and $106\mathrm{GPa}$. Temperature cycling the sample at 87 and $106\mathrm{GPa}$ shows insulating and metallic behavior at these pressures, respectively. Our observations provide strong evidence for a pressure-induced insulator-to-metal transition beginning at $90\mathrm{GPa}$.

• Received 28 January 2004

DOI:https://doi.org/10.1103/PhysRevB.69.220101