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Metallic "Ferroelectricity" in the Pyrochlore Cd2Re2O7

I. A. Sergienko·V. Keppens·M. McGuire·R. Jin·J. He·S. H. Curnoe·B. C. Sales·P. Blaha·D. J. Singh·K. Schwarz·D. Mandrus
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Abstract

A class of materials known as ``ferroelectric metals'' was discussed theoretically by Anderson and Blount in 1965 [Phys. Rev. Lett. 14, 217 (1965)], but to date no examples of this class have been reported. Here we present measurements of the elastic moduli of Cd2Re2O7 through the 200 K cubic-to-tetragonal phase transition. A Landau analysis of the moduli reveals that the transition is consistent with Cd2Re2O7 being classified as a ``ferroelectric metal'' in the weaker sense described by Anderson and Blount (loss of a center of symmetry). First-principles calculations of the lattice instabilities indicate that the dominant lattice instability corresponds to a two-fold degenerate mode with Eu symmetry, and that motions of the O ions forming the O octahedra dominate the energetics of the transition.

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I. A. Sergienko, V. Keppens, M. McGuire, R. Jin, J. He, S. H. Curnoe, B. C. Sales, P. Blaha, D. J. Singh, K. Schwarz, D. Mandrus. 2004-02-05. Metallic "Ferroelectricity" in the Pyrochlore Cd2Re2O7. https://doi.org/10.1103/physrevlett.92.065501

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