Pressure-induced melting of charge-order in the self-doped Mott insulator YNiO3 -: art. no. 094106

The stability under pressure of charge order (Ni3+delta/Ni3-delta) in YNiO3 has been investigated by infrared spectroscopy and x-ray synchrotron diffraction studies up to 23 GPa. We report the observation of a sudden electronic and structural transition in the pressure dependence of YNiO3 at approximate to14 GPa. The pressure-induced lattice evolution is consistent with a P2(1)/n to Pbnm structural transformation similar to the previously reported thermal melting of the charge-ordered state. Phonon screening indicating rapid electron hopping in the high-pressure phase has been observed from infrared measurements. However, although the conductivity increases due to partial charge delocalization, a metallic phase was not confirmed above the pressure-induced transition.