Cuprate superconductors as anomalous metallic states near the Mott insulator

Spin and charge responses of the normal state in the cuprates are analyzed in terms of a state close to the Mott insulator. An anomalous feature of the cuprates is demonstrated from a general theory of the Mott transition. A remarkable crossover between a single- and a multi-component carrier system and its consequences in the cuprates is discussed. A phenomenological theory of the spin correlation is also constructed based on the fact that the spin correlation has a characteristic correlation length inversely proportional to the doping concentration with an insensitive temperature dependence. The NMR and the neutron data of the cuprates are both accounted for by the phenomenological theory.