ハロフォーム・インターカレートC60の構造と,超伝導性特性に及ぼす影響
Robert E Dinnebier1, Olle Gunnarsson, Holger Brumm
1Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
まとめ
C60.CHCl3やC60.CHBr3のようなフルレン化合物の超伝導性は117Kに達する.構造分析は格子膨張を明らかにするが,帯構造の計算は,これだけでは高い移行温度を説明できないことを示唆する.
科学分野:
- 材料科学 材料科学とは
- 凝縮物質物理学 凝縮物質物理学
- 固体化学 固体化学
背景:
- フルレレン化合物,特にCHCl3とCHBr3と交差したC60は,高い超伝導的移行温度 (Tc) を表しています.
- これらの材料でこれまでに発見された最大117KのTcは,重要な科学的関心を呼び起こしています.
- この超伝導性を支配する構造的および電子的要因を理解することは,材料の開発において極めて重要です.
研究 の 目的:
- CHCl3とCHBr3の結晶構造を,高度な difraktion 技術を用い,C60をインターカレートする.
- 電子帯の構造とフェルミレベルでの状態の密度を調査する.
- 構造的変更,電子特性,および観測された高い超伝導的移行温度との関係を明らかにする.
主な方法:
- シンクロトロンX線粉末 difraktionは,クリスタル構造を正確に決定するために使用されました.
- 緊密に結合する帯状構造の計算は,インターケラされたフルレネの表面層のために行われました.
- 分析は,フェルミエネルギーにおける状態の格子膨張,分子配置,電子密度に焦点を当てた.
主要な成果:
- 結晶構造は,主にトリクリニックb軸に沿って,重要な格子膨張を明らかにします.
- C60分子は,構造の中で約六角形,わずかに拡張された格子を形成します.
- バンド構造の計算は,C60.2CHCl3とC60.2CHBr3のフェルミエネルギーでの状態の密度が,原始C60と比較して,特に高いTcに関連したドーピングで減少していることを示しています.
結論:
- CHCl3とCHBr3が交差したC60における格子膨張は,アニソトロピー的に発生する.
- 観測された高い超伝導体移行温度は,格子膨張にのみ帰属することはできません.
- フェルミレベルでの状態の密度などの電子的要因は,重要な役割を果たし,強化された超伝導性を完全に説明するためにさらなる調査を必要とします.
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