Pressure-induced metal-insulator transition in the spin-orbit Mott insulator Ba₂IrO₄

Electronic transport properties in the spin-orbit Mott insulator Ba ₂IrO₄ were studied under high pressure (P), up to 15 GPa. Resistivity measurements revealed a metal-insulator (M-I) transition at 13.8 GPa in Ba₂IrO₄. In the insulating state (P<13.8 GPa), the resistivity well follows the variable-range-hopping regime, suggesting that the carrier conduction is dominated by Anderson localization. In the metallic state (P<13.8 GPa), non-Fermi-liquid behavior was observed at low temperature. Ba₂IrO₄ exhibits an unconventional critical exponent (δ=1-2) at the M-I transition. These results suggest that Ba ₂IrO₄ has an unusual electronic state affected by the "marginal quantum critical point (MQCP)."