title: Spontaneous formation of zigzag chains at the metal-insulator transition in the β-pyrochlore CsW2O6.
abstract: A paramagnetic metal to nonmagnetic insulator transition at T(MIT)=210 K is reported for the β-pyrochlore oxide CsW(2)O(6), accompanied by a first order structural transition that creates <110> oriented chains in the pyrochlore lattice. Comparison of CsW(2)O(6), which has 1 electron per 2 W sites, to the fully d(0) analog CsTaWO(6) shows that the transitions are electronically driven. Corefinement of high resolution synchrotron x-ray and neutron diffraction data shows that the structural distortion that creates the W chains cannot be attributed to simple charge or orbital ordering. Density functional theory calculations suggest that the phase transition is driven by a sharply peaked electronic density of states near the Fermi energy in the cubic β-pyrochlore phase. A further electronic instability is required to create the insulating ground state.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Daigorou
authors.initials: D
authors.lastname: Hirai
authors.forename: Martin
authors.initials: M
authors.lastname: Bremholm
authors.forename: Jared M
authors.initials: JM
authors.lastname: Allred
authors.forename: Jason
authors.initials: J
authors.lastname: Krizan
authors.forename: Leslie M
authors.initials: LM
authors.lastname: Schoop
authors.forename: Qing
authors.initials: Q
authors.lastname: Huang
authors.forename: Jing
authors.initials: J
authors.lastname: Tao
authors.forename: R J
authors.initials: RJ
authors.lastname: Cava