High pressure synthesis of a new perovskite-type cuprate with doped Cu-O chains*

The discovery of high-temperature superconductivity in cuprates has spurred the search for novel low-dimensional cuprates such as spin-ladder compounds. On the other hand, less attention has been paid for the three-dimensional counterpart, the perovskite-type cuprates ACuO₃, presumably because of the difficulty in high-pressure synthesis. In this study, we have succeeded in the high-pressure synthesis of a novel GdFeO₃-type perovskite cuprate PrCuO₃ with quasi-one-dimensional Cu-O chains showing nearly metallic conductivity. Synchrotron x-ray diffraction and x-ray absorption spectroscopy reveal that the oxidation state can be described as Pr^(4-δ)+Cu^(2+δ)+O₃. The first principles calculations suggest that the formation of the Cu-O chain is caused by the A-B site charge transfer and the cooperative Jahn-Teller distortion of nearly divalent Cu ions. This system offers a unique opportunity to explore novel quantum phases of correlated electrons as the simplest one-dimensional counterpart of the high-temperature superconducting cuprates.