Plasmonic nanostar photocathodes for optically-controlled directional currents
Plasmonic nanostar photocathodes for optically-controlled directional currents
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DOI：
10.1038/s41467-020-15115-0
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发表时间：
2020-03-13
影响因子：
16.6
通讯作者：
Nesbitt, David J.
中科院分区：
文献类型：
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作者：
Pettine, Jacob;Choo, Priscilla;Nesbitt, David J.
等离子体纳米阴极为纳米电子器件和脉冲电子源中的飞秒光电流的光学驱动、切换和转向提供了独特的机会。然而，纳米等离子体激元系统中的角光电流分布仍然知之甚少，因此难以预测和控制。在这里，我们提供了一个直接的动量空间表征等离子体金纳米星的多光子光电发射，并展示了这些电流的全光学控制。通过激光频率或线性偏振选择性地激发单个纳米星上的不同尖端来实现多功能角度控制，从而旋转尖端对准的定向光电发射，如用角度分辨的2D速度映射和3D重建所观察到的。经典的等离子体场模拟结合量子光电发射理论阐明了表面介导的非线性激发等离子体场增强高度集中在尖锐的尖端（R-尖端= 3.4 nm）的作用。因此，我们建立了一个简单的机制，飞秒时空电流控制在设计师纳米系统。
Plasmonic nanocathodes offer unique opportunities for optically driving, switching, and steering femtosecond photocurrents in nanoelectronic devices and pulsed electron sources. However, angular photocurrent distributions in nanoplasmonic systems remain poorly understood and are therefore difficult to anticipate and control. Here, we provide a direct momentum-space characterization of multiphoton photoemission from plasmonic gold nanostars and demonstrate all-optical control over these currents. Versatile angular control is achieved by selectively exciting different tips on single nanostars via laser frequency or linear polarization, thereby rotating the tip-aligned directional photoemission as observed with angle-resolved 2D velocity mapping and 3D reconstruction. Classical plasmonic field simulations combined with quantum photoemission theory elucidate the role of surface-mediated nonlinear excitation for plasmonic field enhancements highly concentrated at the sharp tips (R-tip = 3.4 nm). We thus establish a simple mechanism for femtosecond spatiotemporal current control in designer nanosystems.