A variety of applications rely on the efficient generation of hot carriers within metal nanoparticles and charge transfer to surrounding molecules or materials. The optimization of such processes requires a detailed understanding of excited carrier spatial, temporal, and momentum distributions, which also leads to opportunities for active optical control over hot carrier dynamics on nanometer and femtosecond scales. Such capabilities are emerging in nanoplasmonic systems and typically rely on tuning optical polarization and/or frequency to selectively excite one or more discrete hot spots defined by the particle geometry. Here, we introduce a unique case in which hot electron excitation and emission distributions can instead be continuously controlled via linear laser polarization in the azimuthal plane of a gold nanoshell supported on a substrate. In this configuration, it is the laser field that breaks the azimuthal symmetry of the supported nanoshell and determines the plasmonic field distribution. Using angle-resolved photoelectron velocity map imaging, we find that the hot electrons are predominantly emitted orthogonal to the nanoshell dipolar surface plasmon resonance axis defined by the laser polarization. Furthermore, such anisotropic emission is only observed for nanoshells, while solid gold nanospheres are found to be isotropic emitters. We show that all of these effects are recapitulated via simulation of the plasmonic electric field distributions within the nanoparticle volume and ballistic Monte Carlo modeling of the hot electron dynamics. These results demonstrate a highly predictive level of understanding of the underlying physics and possibilities for ultrafast spatiotemporal control over hot carrier dynamics.

中文翻译：

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从各向同性金纳米壳各向异性光发射的连续角度控制。

各种应用都依赖于在金属纳米颗粒中高效生成热载流子，并将电荷转移到周围的分子或材料中。这种过程的优化需要对激发的载流子的空间，时间和动量分布有详细的了解，这也为在纳米级和飞秒级的热载流子动力学上进行主动光学控制提供了机会。这样的能力在纳米等离子体系统中正在出现，并且通常依赖于调谐光学偏振和/或频率以选择性地激发由粒子几何形状限定的一个或多个离散热点。在这里，我们介绍一种独特的情况，其中热电子的激发和发射分布可以通过线性激光偏振在衬底上支撑的金纳米壳的方位角平面内进行连续控制。在这种配置中，正是激光场破坏了所支撑纳米壳的方位对称性并确定了等离子体场分布。使用角度分辨光电子速度图成像，我们发现热电子主要发射正交于由激光偏振定义的纳米壳偶极表面等离激元共振轴。此外，仅在纳米壳中观察到这种各向异性发射，而发现固态金纳米球是各向同性发射体。我们表明，通过模拟纳米粒子体积内的等离子电场分布和热电子动力学的弹道蒙特卡洛模型，可以概括所有这些效应。