Comprehensive suppression of single-molecule conductance using destructive σ-interference
Comprehensive suppression of single-molecule conductance using destructive σ-interference
复制标题
利用破坏性γ干扰全面抑制单分子电导
DOI：
10.1038/s41586-018-0197-9
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发表时间：
2018-06-21
期刊：
影响因子：
64.8
通讯作者：
Solomon, Gemma C.
中科院分区：
文献类型：
--
作者：
Garner, Marc H.;Li, Haixing;Solomon, Gemma C.
电子通过分子（以及通过任何纳米级绝缘和介电材料（1））的隧穿显示出随着长度增加的指数衰减（2），长度依赖性反映在电子承载电流的能力中。最近证明（3-5），通过分子结的相干隧穿也可以被相消量子干涉（6）抑制，这是一种不依赖于长度的机制。对于先前研究的碳基分子，取消所有传输通道将涉及抑制来自π轨道和σ轨道系统的电流贡献。先前关于相消干涉的报告已经证明了仅通过π通道的传输的减少。在这里，我们报告了一个饱和的硅基分子与官能化的双环[2.2.2] octasilane部分，表现出破坏性的量子干涉在其西格玛系统。虽然分子硅通常形成导线，我们使用电导测量和从头计算的组合来表明，破坏性的σ-干涉，这里通过锁定到重叠的构象内的双环分子框架的硅-硅键，可以产生非常绝缘的分子长度小于一纳米。我们的分子还表现出异常高的热功率（每开尔文0.97毫伏），这是通过相消干涉抑制所有隧穿路径的进一步实验特征：计算表明，中心双环[2.2.2]辛硅烷单元的导电性低于其占据的空白空间。这里提出的分子设计提供了一个基于量子干涉的单分子绝缘体方法的概念验证。
The tunnelling of electrons through molecules (and through any nanoscale insulating and dielectric material(1)) shows exponential attenuation with increasing length(2), a length dependence that is reflected in the ability of the electrons to carry an electrical current. It was recently demonstrated(3-5) that coherent tunnelling through a molecular junction can also be suppressed by destructive quantum interference(6), a mechanism that is not length-dependent. For the carbon-based molecules studied previously, cancelling all transmission channels would involve the suppression of contributions to the current from both the pi-orbital and sigma-orbital systems. Previous reports of destructive interference have demonstrated a decrease in transmission only through the pi-channel. Here we report a saturated silicon-based molecule with a functionalized bicyclo [2.2.2] octasilane moiety that exhibits destructive quantum interference in its sigma-system. Although molecular silicon typically forms conducting wires, we use a combination of conductance measurements and ab initio calculations to show that destructive sigma-interference, achieved here by locking the silicon-silicon bonds into eclipsed conformations within a bicyclic molecular framework, can yield extremely insulating molecules less than a nanometre in length. Our molecules also exhibit an unusually high thermopower (0.97 millivolts per kelvin), which is a further experimental signature of the suppression of all tunnelling paths by destructive interference: calculations indicate that the central bicyclo[2.2.2]octasilane unit is rendered less conductive than the empty space it occupies. The molecular design presented here provides a proof-of-concept for a quantum-interference-based approach to single-molecule insulators.