title: Spin-driven jahn-teller distortion in a pyrochlore system
abstract: The ground-state properties of the spin-1 antiferromagnetic Heisenberg model on the corner-sharing tetrahedra, the pyrochlore lattice, are investigated. By breaking up each spin into a pair of 1/2-spins, the problem is reduced to the equivalent one of the spin-1/2 tetrahedral network in analogy with the valence bond solid state in one dimension. The twofold degeneracy of the spin singlets of a tetrahedron is lifted by a Jahn-Teller mechanism, leading to a cubic to tetragonal structural transition. It is proposed that the present mechanism is responsible for the phase transition observed in the spin-1 spinel compounds ZnV2O4 and MgV2O4.
authors: Institute for Solid State Physics, University of Tokyo, Kashiwa-no-ha 5-1-5, Kashiwa-si, Chiba 277-8581, Japan.
authors: Y
authors: Yamashita
authors: K
authors: Ueda