I. Sega

Magnetic fluctuations and resonant peak in cuprates: Towards a microscopic theory

Magnetic fluctuations and evolution of the resonant peak with doping in superconducting cuprates are studied within the planar t-J model. The analysis is based on the equations of motion for spins and the memory-function approach to dynamics of magnetic response where the main damping of the low-energy spin collective mode comes from the decay into fermionic degrees of freedom. In general the normal-state damping is large, leading to a overdamped collective mode. At an intermediate doping in the superconducting phase, a d-wave gap leads to a sharp resonant peak with reduced intensity and downward dispersion. At low doping the damping function is closely related to the c-axis optical conductivity, and the resonant-peak behavior is determined by two energy scales: the pseudogap and the coherent superconducting gap.

Scaling of the magnetic response in doped antiferromagnets.

A theory of the anomalous omega/T scaling of the dynamic magnetic response in cuprates at low doping is presented. It is based on the memory function representation of the dynamical spin susceptibility in a doped antiferromagnet where the damping of the collective mode is constant and large, whereas the equal-time spin correlations saturate at low T. Exact diagonalization results within the t-J model are shown to support assumptions. Consequences, for both the scaling function and the normalization amplitude, are well in agreement with neutron scattering results.

C-AXIS CONDUCTIVITY IN THE NORMAL STATE OF CUPRATE SUPERCONDUCTORS

The

Entanglement of two delocalized electrons

c

High-Doping Regime in a Planar Model for Strongly Correlated Electrons

-axis optical conductivity and dc resistivity are calculated within the

Electron momentum distribution in underdoped cuprates

t

GROUND STATE PROPERTIES IN THE T-J MODEL AT HIGH DOPING

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Spin fluctuations in cuprates as the key to high Tc

J

Spectral Properties of Underdoped Cuprates

model assuming that the interlayer hopping is incoherent. Use is made of numerical results for spectral functions recently obtained with the finite-temperature Lanczos method for finite two-dimensional systems. In the optimally doped regime we find an anomalous relaxation rate

Freezing of spin dynamics and ω/T scaling in underdoped cuprates

{\ensuremath{\tau}}_{c}^{\ensuremath{-}1}\ensuremath{\propto}\ensuremath{\omega}+{\ensuremath{\xi}}_{c}T