173 research outputs found
Interplay of charge, spin, orbital and lattice correlations in colossal magnetoresistance manganites
We derive a realistic microscopic model for doped colossal magnetoresistance
manganites, which includes the dynamics of charge, spin, orbital and lattice
degrees of freedom on a quantum mechanical level. The model respects the SU(2)
spin symmetry and the full multiplet structure of the manganese ions within the
cubic lattice. Concentrating on the hole doped domain () we
study the influence of the electron-lattice interaction on spin and orbital
correlations by means of exact diagonalisation techniques. We find that the
lattice can cause a considerable suppression of the coupling between spin and
orbital degrees of freedom and show how changes in the magnetic correlations
are reflected in dynamic phonon correlations. In addition, our calculation
gives detailed insights into orbital correlations and demonstrates the
possibility of complex orbital states.Comment: 8 pages, 12 figures; more detailed versio
Local distribution approach to disordered binary alloys
We study the electronic structure of the binary alloy and (quantum)
percolation model. Our study is based on a self-consistent scheme for the
distribution of local Green functions. We obtain detailed results for the
density of states, from which the phase diagram of the binary alloy model is
constructed, and discuss the existence of a quantum percolation threshold.Comment: 9 pages, 8 figures. A few minor changes, 1 figure adde
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