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Structural instability of two- and three-dimensional pyrochlore spin lattices in high magnetic fields

Oleg Derzhko, Johannes Richter

cond-mat.str-elarXiv:cond-mat/0507538

Abstract

We consider the quantum spin-s XXZ Heisenberg antiferromagnet on the two- and three-dimensional pyrochlore lattices and examine a spin-Peierls mechanism of lowering the total energy by a lattice distortion in a high magnetic field. For the exact eigenstates consisting of several independent localized magnons in a ferromagnetic environment we show the existence of a spin-Peierls instability by rigorous analytical calculations. In addition we report on exact diagonalization data for finite two-dimensional pyrochlore lattices up to N=64 sites. We discuss a scenario of the field-tuned changes in the ground-state properties of the frustrated spin lattices due to the coupling between spin and lattice degrees of freedom.

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