The Morphology of Narrow Gaps Modifies the Plasmonic Response
The Morphology of Narrow Gaps Modifies the Plasmonic Response
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DOI：
10.1021/ph5004016
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发表时间：
2015-02-01
期刊：
影响因子：
7
通讯作者：
Aizpurua, Javier
中科院分区：
文献类型：
--
作者：
Esteban, Ruben;Aguirregabiria, Garikoitz;Aizpurua, Javier
等离子体间隙天线的光学响应主要由天线的两个组成臂的库仑相互作用决定。使用严格的计算支持简单的分析模型，我们观察到如何纳米间隙的形态分离两个金属棒显着修改等离子体响应。在圆形终端的情况下，在差距，一组传统的键合模式被发现，强烈的红移减少分离。然而，在平坦表面的情况下，一个明显不同的情况下，发现与两组模式的外观：（i）强烈辐射的纵向天线等离子体激元（LAPs），表现出饱和的非常窄的间隙的红移，和（ii）横向腔等离子体激元（TCP）局限于差距，这是弱辐射和强烈依赖于两个臂之间的分离距离。这两组模式可以独立调谐，提供天线近场和远场响应的详细控制。我们说明这些属性也与应用程序较大的红外线间隙天线的极性材料，如SiC。最后，我们使用量子校正模型（QCM）表明，差距的形态对等离子体响应也有显着的影响亚纳米间隙。这种效应对于正确解释金属腔中的电荷转移过程至关重要，其中电子隧穿等量子效应很重要。
The optical response of a plasmonic gap-antenna is mainly determined by the Coulomb interaction of the two constituent arms of the antenna. Using rigorous calculations supported by simple analytical models, we observe how the morphology of a nanometric gap separating two metallic rods dramatically modifies the plasmonic response. In the case of rounded terminations at the gap, a conventional set of bonding modes is found that red-shifts strongly with decreasing separation. However, in the case of flat surfaces, a distinctly different situation is found with the appearance of two sets of modes: (i) strongly radiating longitudinal antenna plasmons (LAPs), which exhibit a red-shift that saturates for very narrow gaps, and (ii) transverse cavity plasmons (TCPs) confined to the gap, which are weakly radiative and strongly dependent on the separation distance between the two arms. The two sets of modes can be independently tuned, providing detailed control of both the near- and far-field response of the antenna. We illustrate these properties also with an application to larger infrared gap-antennas made of polar materials such as SiC. Finally we use the quantum corrected model (QCM) to show that the morphology of the gap has a dramatic influence on the plasmonic response also for subnanometer gaps. This effect can be crucial for the correct interpretation of charge transfer processes in metallic cavities where quantum effects such as electron tunneling are important.