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arXiv · 1009.0355

Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure

Hiroki Ogusu·Nao Takeshita·Koichi Izawa·Jun-ichi Yamaura·Yasuo Ohishi·Satoshi Tsutsui·Yoshihiko Okamoto·Zenji Hiroi
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Abstract

Rattling-induced superconductivity in the β-pyrochlore oxide KOs2O6 is investigated under high pressure up to 5 GPa. Resistivity measurements in a high-quality single crystal reveal a gradual decrease in the superconducting transition temperature Tc from 9.7 K at 1.0 GPa to 6.5 K at 3.5 GPa, followed by a sudden drop to 3.3 K at 3.6 GPa. Powder X-ray diffraction experiments show a structural transition from cubic to monoclinic or triclinic at a similar pressure. The sudden drop in Tc is ascribed to this structural tran-sition, by which an enhancement in Tc due to a strong electron-rattler interaction present in the low-pressure cubic phase is abrogated as the rattling of the K ion is completely suppressed or weakened in the high-pressure phase of reduced symmetry. In addition, we find two anomalies in the temperature dependence of resistivity in the low-pressure phase, which may be due to subtle changes in rattling vibration.

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Hiroki Ogusu, Nao Takeshita, Koichi Izawa, Jun-ichi Yamaura, Yasuo Ohishi, Satoshi Tsutsui, Yoshihiko Okamoto, Zenji Hiroi. 2010-09-02. Superconducting and Structural Transitions in the β-Pyrochlore Oxide KOs2O6 under High Pressure. https://doi.org/10.1143/jpsj.79.114710

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