Absence of charge order in the dimerized κ-phase BEDT-TTF salts
Absence of charge order in the dimerized κ-phase BEDT-TTF salts
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DOI：
10.1103/physrevb.86.245103
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发表时间：
2012-12-06
影响因子：
3.7
通讯作者：
Dressel, Martin
中科院分区：
文献类型：
--
作者：
Sedlmeier, Katrin;Elsaesser, Sebastian;Dressel, Martin
利用红外振动光谱，我们研究了二聚的二维有机盐，以寻找可能的电荷重新分布，可能构成电子偶极子和铁电性：量子自旋液体κ-（BEDT-TTF）（2）Cu-2（CN）（3）[BEDT-TTF：二-（亚乙基二硫代）四硫富瓦烯]，反铁磁莫特绝缘体kappa-（BEDT-TTF）（2）Cu[N（CN）（2）]Cl和超导体kappa-（BEDT-TTF）（2）Cu[N（CN）（2）]Br。它们中没有一个显示出电荷分离的迹象。在冷却至低温时，所有BEDT-TTF分子在+/-0.005e内保持均匀带电。在T = 6 K附近没有观察到电荷分布的改变，其中已经报道了自旋液体材料kappa-（BEDT-TTF）（2）Cu-2（CN）（3）的低温异常。在该化合物中，面内光学响应和振动耦合是相当各向异性的，这表明BEDT-TTF分子在c方向上的倾斜以及它们与阴离子层的耦合在解释电磁性质时必须考虑。
Utilizing infrared vibrational spectroscopy we have investigated dimerized two-dimensional organic salts in order to search for possible charge redistribution that might constitute electronic dipoles and ferroelectricity: the quantum spin liquid kappa-(BEDT-TTF)(2)Cu-2(CN)(3) [BEDT-TTF: bis-(ethylenedithio)tetrathiafulvalene], the antiferromagnetic Mott insulator kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, and the superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. None of them exhibit any indication of charge disproportionation. Upon cooling to low temperatures all BEDT-TTF molecules remain homogeneously charged within +/- 0.005e. No modification in the charge distribution is observed around T = 6 K where a low-temperature anomaly has been reported for the spin-liquid material kappa-(BEDT-TTF)(2)Cu-2(CN)(3). In this compound the in-plane optical response and vibrational coupling are rather anisotropic, indicating that the tilt of the BEDT-TTF molecules in c direction and their coupling to the anion layers has to be considered in the explanation of the electromagnetic properties.