Charge ordering in θ-(BEDT-TTF)2RbZn(SCN)4 studied by vibrational spectroscopy
Charge ordering in θ-(BEDT-TTF)2RbZn(SCN)4 studied by vibrational spectroscopy
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通过振动光谱研究 θ-(BEDT-TTF)2RbZn(SCN)4 中的电荷排序
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
A. Kawamoto
中科院分区：
文献类型：
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作者：
Kaoru Yamamoto;K. Yakushi;K. Miyagawa;K. Kanoda;A. Kawamoto
利用偏振拉曼光谱和红外光谱研究了θ-(BEDT-TTF) 2 RbZn(SCN) 4 [BEDT-TTF表示二（乙基烯二硫代）四噻唑烯]绝缘相的电荷分布。在金属-绝缘体转变温度下，拉曼光谱和红外光谱均呈现出多峰模式。我们根据碳取代样品的同位素位移确定了碳双键（C=C）的拉伸模式，并对极化红外光谱和拉曼光谱进行了因子群分析。这些结果证明了绝缘相发生了电荷歧化现象，并且电荷排列的空间格局符合x射线衍射所确定的对称性。根据环C-C拉伸模式的频率估计了CD比，该模式与电子激发态弱耦合。讨论了一种基于振动光谱学的系统研究CD现象的方法。
Charge distribution in the insulating phase of θ-(BEDT-TTF) 2 RbZn(SCN) 4 [BEDT-TTF denotes bis(ethyl-enedithiolo)tetrathiafulvalene] is investigated using the polarized Raman and infrared (IR) spectroscopy. Both of the Raman and IR spectra showed a multiple-peaks pattern below metal-insulator transition temperature. We assigned the carbon-double-bond (C=C) stretching-modes based on the isotope shift in the 1 3 C-substituted sample, and performed a factor-group analysis for the polarized IR and Raman spectra. These results proved that charge disproportionation (CD) takes place in the insulating phase, and that the spatial pattern of the charge ordering agrees with the symmetry determined by the x-ray diffraction. The CD ratio was estimated from the frequency of a ring C-C stretching mode that is weakly coupled with electronic excited states. A systematic way to investigate the CD phenomenon based on vibrational spectroscopy is discussed.