Thermal conductance of single-molecule junctions
Thermal conductance of single-molecule junctions
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DOI：
10.1038/s41586-019-1420-z
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发表时间：
2019-08-29
期刊：
影响因子：
64.8
通讯作者：
Meyhofer, Edgar
中科院分区：
文献类型：
--
作者：
Cui, Longji;Hur, Sunghoon;Meyhofer, Edgar
单分子结已被广泛用于探测原子和分子尺度上的各种性质，如导电（1-3）、发光（4）、热电能量转换（5，6）、量子干涉（7，8）、散热（9，10）和电子噪声（11）。然而，目前感兴趣的一个关键量--单分子结的热导率--还没有直接通过实验确定，这是由于在皮瓦水平上检测微小热流的挑战。在这里，我们展示了先前开发的用于研究单金属原子结的热导率的皮瓦分辨率扫描探针（12），当与时间平均测量方案结合使用以增加信噪比时，也允许量化单分子结的低得多的热导率。我们的实验上的原型Au-烷二硫醇-Au结含有2至10个碳原子证实，热导率是一个第一近似独立的分子长度，与详细的从头计算模拟。我们预计，我们的方法将能够系统地探索许多其他一维系统中的热输运，例如短分子和聚合物链，对于这些系统，热导的计算预测（13-16）仍然无法通过实验获得。
Single-molecule junctions have been extensively used to probe properties as diverse as electrical conduction(1-3), light emission(4), thermoelectric energy conversion(5,6), quantum interference(7,8), heat dissipation( 9,10) and electronic noise(11) at atomic and molecular scales. However, a key quantity of current interest-the thermal conductance of single-molecule junctions-has not yet been directly experimentally determined, owing to the challenge of detecting minute heat currents at the picowatt level. Here we show that picowatt-resolution scanning probes previously developed to study the thermal conductance of single-metal-atom junctions(12), when used in conjunction with a time-averaging measurement scheme to increase the signal-to-noise ratio, also allow quantification of the much lower thermal conductance of single-molecule junctions. Our experiments on prototypical Au-alkanedithiol-Au junctions containing two to ten carbon atoms confirm that thermal conductance is to a first approximation independent of molecular length, consistent with detailed ab initio simulations. We anticipate that our approach will enable systematic exploration of thermal transport in many other one-dimensional systems, such as short molecules and polymer chains, for which computational predictions of thermal conductance(13-16) have remained experimentally inaccessible.