存在原子级缺陷时隧道结的定向皮天线行为
Directional picoantenna behavior of tunnel junctions in the presence of atomic-scale defects
AI总结：
本研究发现扫描隧道显微镜针尖与带单原子台阶的金属表面间的等离子体皮腔具有定向发射特性，可作为皮天线，其方向性源于皮腔等离子体的发光倾斜，为纳米尺度光-物质相互作用调控提供了新途径。
摘要：
等离子体纳米天线是经过尺寸和形状工程设计的金属-介质结构，近年来因可实现对荧光团发射光的方向性和时间特性的调控而备受关注。这类天线利用局域表面等离子体共振（Localized Surface Plasmon Resonances）介导的光-物质相互作用，目前已通过金属纳米颗粒或其他金属纳米结构得到验证。等离子体皮腔，即模式体积低于1立方纳米的等离子体腔，因其极端的场限制效应，可作为天线介导光-物质相互作用，效率甚至优于纳米尺度的同类结构，但其发射的方向性难以调控。本研究中，我们发现扫描隧道显微镜（Scanning Tunnelling Microscope）针尖与带有单原子台阶的金属表面之间形成的等离子体皮腔呈现出定向发射轮廓，因此可被视为皮天线的一种实现。与电磁计算结果的对比表明，观测到的方向性源于皮腔等离子体的发光倾斜效应。我们的研究结果为利用皮天线作为纳米尺度下调控光-物质相互作用的有效途径铺平了道路。
英文摘要：
Plasmonic nanoantennas, metallodielectric structures with engineered size and shape, have attracted much attention lately as they make the control of the directionality and temporal characteristics of light emitted by fluorophores possible. Nanoantennas exploit light-matter interactions mediated by Localized Surface Plasmon Resonances and, so far, have been demonstrated using metallic nanoparticles or other metallic nanostructures. Plasmonic picocavities, i.e., plasmonic cavities with mode volumes below 1 cubic nanometer, could act as antennas to mediate light-matter interaction even more efficiently than their nanoscale counterparts due to their extreme field confinement, but the directionality on their emission is difficult to control. In this work, we show that the plasmonic picocavity formed between the tip of a Scanning Tunnelling Microscope and a metal surface with a monoatomic step shows directional emission profiles and, thus, can be considered as a realization of a picoantenna. Comparison with electromagnetic calculations demonstrates that the observed directionality arises from light emission tilting of the picocavity plasmons. Our results, thus, pave the way to exploiting picoantennas as an efficient way to control light-matter interaction at the nanoscale.
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