Optical investigation of A<i>₂i>Ru<i>₂i>O<i>₇i> (<i>A=Yi>, Tl, and Bi): temperature dependent self-doping effects

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• 作者：Lee ; J.S. ; Lee ; Y.S. ; Kim ; K.W. ; Noh ; T.W. ; Yu ; J. ; Takeda ; Y. ; Kanno ; R.
• 关键词：78.20.<i>&minus ; i>e ; 78.30.<i>&minus ; i>j ; 78.66.<i>&minus ; i>w ; Pyrochlore ruthenates ; Self-doping ; Optical conductivity spectra
• 刊名：Physica C
• 出版年：2001
• 期刊代码：80_09214534
• 类别：ms
• 出版时间：November, 2001
• 卷：364-365
• 期：Complete
• 页码：632-635
• 文件大小：175 K

摘要

We measured the temperature (<i>Ti>-) dependent optical conductivity spectra <i>σ(ω)i> of Y<i>₂i>Ru<i>₂i>O<i>₇i> (insulating), Tl<i>₂i>Ru<i>₂i>O<i>₇i> (metal–insulator transition) and Bi<i>₂i>Ru<i>₂i>O<i>₇i> (metallic). <i>σ(ω)i> of Y<i>₂i>Ru<i>₂i>O<i>₇i> show absorption peaks around 1.7 and 3.2 eV, which are nearly <i>Ti>-independent. <i>σ(ω)i> of Bi<i>₂i>Ru<i>₂i>O<i>₇i> are also nearly <i>Ti>-independent, but have a Drude-like peak in the far-infrared (IR) region. On the other hand, <i>σ(ω)i> of Tl<i>₂i>Ru<i>₂i>O<i>₇i> have a very strong mid-IR peak, and its spectral weight is strongly <i>Ti>-dependent. Its <i>Ti> dependence through the metal–insulator transition is quite similar to the doping dependence of doped transition metal oxides, but there is no external dopant in Tl<i>₂i>Ru<i>₂i>O<i>₇i>. Therefore, these phenomena of Tl<i>₂i>Ru<i>₂i>O<i>₇i> can be interpreted in terms of <i>Ti>-dependent self-doping effects; namely, the electronic structures near the Fermi level change due to the self-doping for the Ru 4d state in the presence of an easily polarizable Tl ion.