Pressure-induced metal-insulator transition of the mott insulator Ba2IrO4

The electrical resistivity of single crystals of the spin-orbit Mott insulator Ba2IrO4 has been measured at pressures up to 30 GPa and at temperatures from 100 mK to 300 K. Ba2IrO4 shows a metal-insulator transition at around P (c) = 24 GPa, though it does not show superconductivity down to 100 mK. The low-temperature resistivity in the metallic state does not obey a conventional Fermi-liquid description. This suggests that carriers are incoherently scattered by antiferromagnetic quantum spin fluctuations. The critical exponent delta for the metal-insulator transition is about 1.6, indicating that Ba2IrO4 is located near the boundary between a Mott and an Anderson insulator. This means that even in a single crystal, the effect of crystallographic disorder should not be ignored.