Electronic properties of correlated metals in the vicinity of a charge-order transition: Optical spectroscopy ofα−(BEDT−TTF)2MHg(SCN)4(M=NH4, Rb, Tl)
Electronic properties of correlated metals in the vicinity of a charge-order transition: Optical spectroscopy ofα−(BEDT−TTF)2MHg(SCN)4(M=NH4, Rb, Tl)
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电荷级跃迁附近相关金属的电子性质：α−(BEDT−TTF)2MHg(SCN)4(M=NH4, Rb, Tl) 的光谱
DOI：
10.1103/physrevb.74.235121
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发表时间：
2006
影响因子：
3.7
通讯作者：
J. Schlueter
中科院分区：
文献类型：
--
作者：
N. Drichko;M. Dressel;C. Kuntscher;A. Pashkin;A. Greco;J. Merino;J. Schlueter
为了研究四分之一填充金属中电子关联的影响，在50 ~ 7000 cm-2范围内测量了准二维有机导体$alpha$-（BEDT-TTF）$2$$M$Hg（SCN）$4 $（$M$ = NH $4 $，Rb，Tl）的红外光谱.在T=300 K时，通过测量$\alpha$-（BEDT-TTF）$2KHg（SCN）$4 $的压力依赖反射率，证实了电子光谱的解释。当从NH $_4 $盐到Rb并进一步到Tl化合物时，电荷顺序波动的特征变得更加明显。随着温度的降低，NH_4 ~+和Rb盐的光学响应的金属特征增强，有效质量减小。对于铊化合物，尽管金属性质仍然占主导地位，但发现了明显的电荷顺序特征。从电子散射率的温度依赖性的交叉温度估计低于相干电荷载流子响应集。的意见是在最近的理论预测的四分之一充满金属系统接近电荷顺序非常一致。
The infrared spectra of the quasi-two-dimensional organic conductors $\alpha$-(BEDT-TTF)$_2$$M$Hg(SCN)$_4$ ($M$ = NH$_4$, Rb, Tl) were measured in the range from 50 to 7000 \cm down to low temperatures in order to explore the influence of electronic correlations in quarter-filled metals. The interpretation of electronic spectra was confirmed by measurements of pressure dependant reflectance of $\alpha$-(BEDT-TTF)$_2$KHg(SCN)$_4$ at T=300 K. The signatures of charge order fluctuations become more pronounced when going from the NH$_4$ salt to Rb and further to Tl compounds. On reducing the temperature, the metallic character of the optical response in the NH$_4$ and Rb salts increases, and the effective mass diminishes. For the Tl compound, clear signatures of charge order are found albeit the metallic properties still dominate. From the temperature dependence of the electronic scattering rate the crossover temperature is estimated below which the coherent charge-carriers response sets in. The observations are in excellent agreement with recent theoretical predictions for a quarter-filled metallic system close to charge order.