Spontaneous Formation of Zigzag Chains at the Metal-Insulator Transition in the $\ensuremath{\beta}$-Pyrochlore ${\mathrm{CsW}}_{2}{\mathbf{O}}_{6}$

Spontaneous Formation of Zigzag Chains at the Metal-Insulator Transition in the $β$ -Pyrochlore ${CsW}_{2} O_{6}$

Daigorou Hirai, Martin Bremholm, Jared M. Allred, Jason Krizan, Leslie M. Schoop, Qing Huang, Jing Tao, and R. J. Cava

Phys. Rev. Lett. 110, 166402 – Published 16 April 2013

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.

Received 3 January 2013

DOI:https://doi.org/10.1103/PhysRevLett.110.166402

Authors & Affiliations

Daigorou Hirai^1,*, Martin Bremholm^1,†, Jared M. Allred^1,‡, Jason Krizan¹, Leslie M. Schoop¹, Qing Huang², Jing Tao³, and R. J. Cava¹

¹Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
²NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
³Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA

^*Present address: Department of Physics, University of Tokyo, Hongo 7-3-1 Tokyo 113-0033, Japan.
^†Present address: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Aarhus C, DK-8000, Denmark.
^‡Present address: Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439, USA.