Abstract: | Copper-oxide (cuprate) high-temperature superconductors are doped Mott insulators. The undoped parent compounds are antiferromagnetic insulators, and superconductivity occurs only when an appropriate number of charge carriers (electrons or holes) are introduced by doping. All cuprate materials contain CuO2 planes (Figure 1a) in their crystal structure; the doped carriers are believed to go into these CuO2 planes, which are responsible for high-temperature superconductivity. High-temperature superconductors are characterized by their unusual physical properties, both in the superconducting state (below the superconducting transition temperature Tc) and in the normal state (above Tc). Since the discovery of high-temperature superconductivity in 1986 1], these unusual physical properties and the mechanism of superconductivity have been prominent issues in condensed matter physics 2]. |