Spin dynamics of high- Tc cuprates in the metallic state as a result of dual itinerant-localized nature of magnetism in strongly correlated CuO 2 plane (YBa 2Cu 3O 6+ x)

Abstract

Spin dynamics in cuprates is analysed in the framework of a new theory (based on the t- t′- J model and the diagrammatic technique for Hubbard operators) developed to treat correctly strong electron correlations within the CuO 2 plane. The dynamic magnetic susceptibility is determined by two contributions different in nature, the “localized” and “itinerant” ones. The “itinerant” contribution reflects a response in the spin susceptibility on Cu related to the propagating carrier quasiparticles. The “localized” contribution reflects the existence of short-range correlations between localized spins. As a result of their competition, the spin dynamics evolves continuously within the metallic state from a normal-metal behaviour at high doping (overdoped regime) to a quantum spindashliquid-type dynamics with magnondashlike excitations at low doping through a nondashFermi-liquid behaviour in all intermediate regimes. The picture of the spin dynamics in the metallic state of YBa 2Cu 3O 6+ x as a whole and in details in relation to INS and NMR experimental data is presented. Many exotic features of χ( k, ω) reveale by these experiments find a natural explanation within the proposed scenario.