F. Onufrieva et J. Rossatmignod, THEORY OF SPIN DYNAMICS IN HIGH-T-C COPPER-OXIDE SUPERCONDUCTORS - APPLICATION TO NEUTRON-SCATTERING, Physical review. B, Condensed matter, 52(10), 1995, pp. 7572-7603
A theory of spin dynamics in copper oxide superconductors is developed
. The theory is based on the t-t'-J model and the diagrammatic techniq
ue for Hubbard operators. The dynamic spin susceptibility calculated f
or metallic hole concentrations includes two different contributions.
The ''localized'' contribution arises from the subsystem of localized
Cu spins with quantum short-range correlations. The ''itinerant'' cont
ribution arises from the subsystem of propagating carrier quasiparticl
es. As a result of their competition, the spin dynamics evolves contin
uously within the metallic state from normal-metal behavior at high do
ping (overdoped regime) to quantum spin-liquid-type dynamics with magn
onlike excitations at low doping through non-Fermi-liquid behavior in
all intermediate regimes. Based on the theory, a detailed analysis of
momentum and energy dependences of the dynamic spin susceptibility for
different doping regimes is performed in order to compare the theoret
ical predictions with the experimental results discovered by inelastic
neutron scattering. We are able to understand the strange shape of Im
(c)hi versus omega and its exotic evolution with doping, the existence
of the resonance peak, the gap and pseudogap effects, and many other
unusual features observed for YBa2Cu3O6+x as well as the incommensurat
e and ''gapless'' behavior for La2-xSrxCuO4.