We use the temperature of the structural phase transition to determine the Jahn-Teller (JT) coupling constant in the model derived for LaMnO3 which includes both the superexchange between S = 2 spins and the JT effect. We also investigate the dependence of the exchange constants on the value of the on-site Coulomb element U , and on the orbital ordering. Journal ref.: O. Sikora and A. M. Oleś, ...

A model interaction is proposed in which pairing is caused by a non-local Jahn-Teller (JT)-like instability due to the coupling between planar O states and k = 0 phonons. Apart from pairing, the interaction is found to naturally allow metallic stripe formation. The consequences of the model for supercon-ductivity in the cuprates are discussed. The model is shown to be consistent with numerous s...

A cluster Monte Carlo algorithm for the Ashkin-Teller (AT) model is constructed according to the guidelines of a general scheme for such algorithms. Its dynamical behaviour is tested for the square lattice AT model. We perform simulations on the line of critical points along which the exponents vary continuously, and find that critical slowing down is significantly reduced. We find continuous v...

We show that the presently available data on the Gamow-Teller (GT) strength in mid-f p-shell nuclei are proportional to the product of the numbers of valence protons and neutron holes in the full f p-shell. This observation leads to important insights into the mechanism for GT quenching and to a simple parametrization of the Gamow-Teller strengths important for electron capture by f p-shell nuc...