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arXiv 0704.0368cond-mat.str-el
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低维有机导体(TMTSF)2FSO 3的金属-绝缘体转变红外显微光谱研究

Metal-insulator transition in the low-dimensional organic conductor (TMTSF)2FSO3 probed by infrared microspectroscopy

A. Pashkin, K. Thirunavukkuarasu, Y. -L. Mathis, W. Kang, C. A. Kuntscher

摘要:

本文测量了准一维有机导体(TMTSF)2$SO_3沿(E|| a)和垂直(E|| b ')与堆叠轴的关系作为温度的函数。在与阴离子有序化有关的金属-绝缘体转变之上,光学电导率谱显示出类似Drude的响应。在跃迁以下,约1500 cm-1(185 meV)的能隙打开,导致在光学电导率谱中的相应电荷转移带。的红外活性振动的分析给出了证据的长程晶体结构调制低于转变温度和短程的晶格调制的顺序波动的转变温度以上。此外,我们报告了一个新的红外模式,在710 cm-1左右,具有特殊的温度行为,这是迄今为止尚未观察到的任何其他(TMTSF)2X盐显示金属-绝缘体转变。基于TMTSF分子振动与FSO 3负离子电偶极矩重取向之间的耦合,提出了一个定性模型,以解释新模式的反常行为.

英文摘要:

We present measurements of the infrared response of the quasi-one-dimensional organic conductor (TMTSF)2$SO3 along (E||a) and perpendicular (E||b') to the stacking axis as a function of temperature. Above the metal-insulator transition related to the anion ordering the optical conductivity spectra show a Drude-like response. Below the transition an energy gap of about 1500 cm-1 (185 meV) opens, leading to the corresponding charge transfer band in the optical conductivity spectra. The analysis of the infrared-active vibrations gives evidence for the long-range crystal structure modulation below the transition temperature and for the short-range order fluctuations of the lattice modulation above the transition temperature. Also we report about a new infrared mode at around 710 cm-1 with a peculiar temperature behavior, which has so far not been observed in any other (TMTSF)2X salt showing a metal-insulator transition. A qualitative model based on the coupling between the TMTSF molecule vibration and the reorientation of electrical dipole moment of the FSO3 anion is proposed, in order to explain the anomalous behavior of the new mode.

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