Breaking Down Resonance: Nonlinear Transport and the Breakdown of Coherent Tunneling Models in Single Molecule Junctions
Breaking Down Resonance: Nonlinear Transport and the Breakdown of Coherent Tunneling Models in Single Molecule Junctions
复制标题
打破共振：非线性输运和单分子结中相干隧道模型的打破
DOI：
10.1021/acs.nanolett.9b00316
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发表时间：
2019-04-01
期刊：
影响因子：
10.8
通讯作者：
Venkataraman, Latha
中科院分区：
文献类型：
--
作者：
Fung, E-Dean;Gelbwaser, David;Venkataraman, Latha
单分子电子学领域的前景是揭示一类新型量子器件，该器件利用亚纳米级系统固有的强电子相互作用。在这里，我们使用定制扫描隧道显微镜形成金-分子-金结，并通过电流-电压测量探索电荷传输。我们关注两种分子的共振隧道机制，一种主要是电子导体，另一种主要传导空穴。我们发现，在高偏置状态下，不破裂的结表现出可重复且明显的负微分电阻 (NDR) 样特征，随后出现峰谷比在某些情况下超过 100 的滞后现象。此外，我们发现结破裂和 NDR 都是由分子轨道主导传输的充电引起的，并发现充电在较低偏压下是可逆的，并且随着时间的推移，动力学时间尺度约为数百毫秒。我们认为这些结果无法用现有的电荷传输模型来解释，并且可能需要描述从相干隧道到顺序隧道的转变的理论进展。我们的工作还提出了在高偏置下操作单分子器件以获得高度非线性行为的新规则。
The promise of the field of single-molecule electronics is to reveal a new class of quantum devices that leverages the strong electronic interactions inherent to subnanometer scale systems. Here, we form Au-molecule-Au junctions using a custom scanning tunneling microscope and explore charge transport through current-voltage measurements. We focus on the resonant tunneling regime of two molecules, one that is primarily an electron conductor and one that conducts primarily holes. We find that in the high bias regime, junctions that do not rupture demonstrate reproducible and pronounced negative differential resistance (NDR)-like features followed by hysteresis with peak-to-valley ratios exceeding 100 in some cases. Furthermore, we show that both junction rupture and NDR are induced by charging of the molecular orbital dominating transport and find that the charging is reversible at lower bias and with time with kinetic time scales on the order of hundreds of milliseconds. We argue that these results cannot be explained by existing models of charge transport and likely require theoretical advances describing the transition from coherent to sequential tunneling. Our work also suggests new rules for operating single-molecule devices at high bias to obtain highly nonlinear behavior.