Quasi One-Dimensional Conductors: The Far Infrared Problem
Quasi One-Dimensional Conductors: The Far Infrared Problem
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准一维导体：远红外问题
DOI：
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发表时间：
1987
期刊：
影响因子：
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通讯作者：
T. Timusk
中科院分区：
文献类型：
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作者：
T. Timusk
在金属状态下，准一维导体具有非常高的直流电导率，在某些情况下相当于室温下的纯铜。因此，人们可能会认为它们的光学性质遵循德鲁德自由电子理论，在此理论中，电导率一直等于直流值，直到松弛时间量级的频率。取而代之的是，准一维导体在远红外显示出光学传导性降低的区域。像(TMTSF)2ClO4这样的材料在低温下的直流电导1约为5·105(Ω·cm)-1，而50 cm-1处的光导2仅为几百(Ω·cm)-1。电导率从高到低的变化发生在实验困难的微波区，在这些极限频率下很少有人做过实验。远红外电导被抑制的现象在准一维材料2-7中几乎是普遍存在的。这种现象首先在TTF-TCNQ中被观察到，但随后也在(TMTSF)2X系列化合物中被报道为导电态。这种差异通常被解释为具有以零频率为中心的非常大的有效振子质量的窄集体模。这样的模型表明，低温下的电流是由集合模携带的。
In the metallic state the quasi one-dimensional conductors are characterized by very high values of dc conductivity equaling in some cases pure copper at room temperature. Thus one might expect their optical properties to follow the Drude free electron theory where the conductivity remains equal to the dc value up to a frequency of the order of the relaxation time. Instead the quasi one-dimensional conductors show a region of depressed optical conductivity in the far infrared. The dc conductivity1 at low temperature of a material such as (TMTSF)2ClO4 is of the order of 5·105 (Ω·cm)-1 whereas the optical conductivity2 at 50 cm-1 is only a few hundred (Ω·cm)-1. The change from high to low conductivity occurs in the experi mentally difficult microwave region and very few experiments have been done at these limiting frequencies. The phenomenon of suppressed far infrared conductivity is almost universal in the quasi one-dimensional materials2–7. It was first observed in TTF-TCNQ but subsequently also reported in (TMTSF)2X family of compounds in their conducting state. This discrepancy has been generally explained in terms of a narrow collective mode with a very large effective oscillator mass centered at zero frequency. Such a model implies that the electrical current at low temperature is carried by the collective mode.