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Comprehensive suppression of single-molecule conductance using destructive σ-interference

机译：利用破坏性σ干扰全面抑制单分子电导

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摘要

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.
机译：电子穿过分子（以及穿过任何纳米级绝缘和介电材料（1））的隧穿随着长度（2）的增加而显示出指数衰减，长度的依赖性反映在电子承载电流的能力上。最近证明（3-5），破坏性的量子干涉也可以抑制通过分子结的相干隧穿（6），这种机理与长度无关。对于先前研究的碳基分子，取消所有传输通道将涉及抑制pi轨道和sigma轨道系统对电流的贡献。先前有关破坏性干扰的报道表明，仅通过pi通道的传输有所减少。在这里，我们报告的饱和的硅基分子具有功能化的双环[2.2.2]八硅烷部分，在其sigma系统中表现出破坏性的量子干扰。尽管分子硅通常形成导线，但我们结合使用电导率测量和从头算起的计算来证明，通过在双环分子框架内将硅-硅键锁定为日蚀构象，可以实现破坏性的sigma-interference，可以产生极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），这是通过破坏性干扰抑制所有隧穿路径的进一步实验特征：计算表明，中央双环[2.2.2]八硅烷单元的导电性低于它占据的空白空间。本文介绍的分子设计为单分子绝缘子的基于量子干涉的方法提供了概念验证。

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  • 来源
    《Nature》 |2018年第7710期|415-419|共5页
  • 作者

    Garner Marc H.; Li Haixing; Chen Yan; Su Timothy A.; Shangguan Zhichun; Paley Daniel W.; Liu Taifeng; Ng Fay; Li Hexing; Xiao Shengxiong; Nuckolls Colin; Venkataraman Latha; Solomon Gemma C.;

  • 作者单位

    Univ Copenhagen, Nanosci Ctr, Copenhagen, Denmark;

    Columbia Univ, Dept Appl Phys & Appl Math, New York, NY USA;

    Shanghai Normal Univ, Optoelect Nano Mat & Devices Inst, Key Lab Resource Chem,Educ Minist, Shanghai Key Lab Rare Earth Funct Mat,Dept Chem, Shanghai, Peoples R China;

    Columbia Univ, Dept Chem, New York, NY 10027 USA;

    Shanghai Jiao Tong Univ, Sch Chem & Chem Engn, Shanghai, Peoples R China;

    Columbia Univ, Dept Chem, New York, NY 10027 USA;

    Shanghai Normal Univ, Optoelect Nano Mat & Devices Inst, Key Lab Resource Chem,Educ Minist, Shanghai Key Lab Rare Earth Funct Mat,Dept Chem, Shanghai, Peoples R China;

    Columbia Univ, Dept Chem, New York, NY 10027 USA;

    Shanghai Normal Univ, Optoelect Nano Mat & Devices Inst, Key Lab Resource Chem,Educ Minist, Shanghai Key Lab Rare Earth Funct Mat,Dept Chem, Shanghai, Peoples R China;

    Shanghai Normal Univ, Optoelect Nano Mat & Devices Inst, Key Lab Resource Chem,Educ Minist, Shanghai Key Lab Rare Earth Funct Mat,Dept Chem, Shanghai, Peoples R China;

    Shanghai Normal Univ, Optoelect Nano Mat & Devices Inst, Key Lab Resource Chem,Educ Minist, Shanghai Key Lab Rare Earth Funct Mat,Dept Chem, Shanghai, Peoples R China;

    Columbia Univ, Dept Appl Phys & Appl Math, New York, NY USA;

    Univ Copenhagen, Nanosci Ctr, Copenhagen, Denmark;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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