Observation of charge stripes in cupric oxide

One of the present intensive concerns about the high-temperature supercondu ctors is whether charge stripes are a key to superconductivity. Here we rep ort observation of charge stripes in the simplest copper oxide, CuO, by rea l-space images obtained by electron microscopy. Charge-ordered domains and normal-lattice domains exist alternatively in the vapor-grown single crysta l of CuO. Since CuO consists of the Cu-O bonding, which is a basic material feature for high-T-c cuprates, the discovery of charge stripes in this bas ic compound has important implications for discussing the mechanism of supe rconductivity in complex cuprates.