title: Peierls mechanism of the metal-insulator transition in ferromagnetic hollandite K2Cr8O16.
abstract: Synchrotron x-ray diffraction experiment shows that the metal-insulator transition occurring in a ferromagnetic state of a hollandite K(2)Cr(8)O(16) is accompanied by a structural distortion from the tetragonal I4/m to monoclinic P112(1)/a phase with a √2×√2×1 supercell. Detailed electronic structure calculations demonstrate that the metal-insulator transition is caused by a Peierls instability in the quasi-one-dimensional column structure made of four coupled Cr-O chains running in the c direction, leading to the formation of tetramers of Cr ions below the transition temperature. This provides a rare example of the Peierls transition of fully spin-polarized electron systems.
authors.affiliation: Department of Physics, Chiba University, Chiba 263-8522, Japan.
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authors.lastname: Toriyama
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authors.lastname: Yamaki
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authors.lastname: Nakao
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authors.lastname: Hasegawa
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authors.lastname: Ueda
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authors.lastname: Ushakov
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authors.lastname: Khomskii
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authors.lastname: Streltsov
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authors.lastname: Konishi
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authors.lastname: Ohta