二硫代低聚亚苯基衍生物单分子结的长度依赖电导和热电势
Length-dependent conductance and thermopower in single-molecule junctions of dithiolated oligophenylene derivatives
摘要：
我们从理论上研究了由与金电极接触的二硫羟化低聚苯基组成的金属-分子-金属结中电导和热电势的长度依赖性。我们发现，而电导随分子长度的增加呈指数衰减，热电势线性增加，最近的实验表明。我们还分析了这些传输特性如何可以调整与甲基侧基。我们的结果可以解释考虑由于其电子捐赠字符以及倾斜角依赖的电导和热电势的能级位移。在我们的密度泛函计算的取代基效应的定性特征解释使用紧束缚模型。此外，我们还观察到了作为分子长度的函数的与量子力学相关的偶奇传输通道简并。
英文摘要：
We study theoretically the length dependence of both conductance and thermopower in metal-molecule-metal junctions made up of dithiolated oligophenylenes contacted to gold electrodes. We find that while the conductance decays exponentially with increasing molecular length, the thermopower increases linearly as suggested by recent experiments. We also analyze how these transport properties can be tuned with methyl side groups. Our results can be explained by considering the level shifts due to their electron-donating character as well as the tilt-angle dependence of conductance and thermopower. Qualitative features of the substituent effects in our density-functional calculations are explained using a tight-binding model. In addition, we observe symmetry-related even-odd transmission channel degeneracies as a function of molecular length.
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