Magnetism is a phenomenon that has always captured the imagination of humans. Its
discovery in the western world is attributed to the ancient Greek civilization. More than 2500 …

The spin-½ antiferromagnetic Heisenberg model on a square lattice is used to describe the
dynamics of the spin degrees of freedom of undoped copper oxides. Even though the model …

It is argued that the long-wavelength, low-temperature behavior of a two-dimensional
quantum Heisenberg antiferromagnet can be described by a quantum nonlinear σ model in …

Since the discovery of superconductivity above 30 K by Bednorz and Müller in the La copper
oxide system, the critical temperature has been raised to 90 K in Y Ba 2 Cu 3 O 7 and to 110 …

The authors review the results of a wide variety of experiments on materials such as La 2
CuO 4 and Nd 2 CuO 4 that contain weakly coupled CuO 2 layers. These materials are …

We present the general theory of clean, two-dimensional, quantum Heisenberg
antiferromagnets which are close to the zero-temperature quantum transition between …

We report a comprehensive neutron-scattering study of the evolution of the magnetic
excitations in La 2− x Sr x CuO 4 for 0≤ x≤ 0.04. We first present accurate measurements of …

To gain insight into the behavior of the Hubbard model, we define a SU (n) invariant
generalization of the Hubbard-Heisenberg model and, in the large-n limit, solve it in one …

Moriya's expression for the ringle-bond anisotropic superexchange interaction is shown to
possess an overlooked hidden symmetry, isomorphic to the symmetry of the isotropic case …

A theoretical review is given on high temperature superconductivity in copper oxides
(cuprates) by focusing on the hole doping cases based on the view that it is realized in …