Terahertz control of nanotip photoemission
Terahertz control of nanotip photoemission
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DOI：
10.1038/nphys2974
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发表时间：
2014-06-01
期刊：
影响因子：
19.6
通讯作者：
Ropers, C.
中科院分区：
文献类型：
--
作者：
Wimmer, L.;Herink, G.;Ropers, C.
强电磁场对物质的主动控制越来越重要，在从极紫外到远红外的整个光谱中都有应用。近年来，相稳定太赫兹场在观察和操纵固体中的基本激发方面显示出巨大的潜力（1-3）。另一方面，在气相中，用太赫兹瞬态驱动自由电荷可以深入了解超快电离动力学（4,5）。在纳米结构中开发这种局部增强太赫兹场的方法，将创造出在纳米尺度上控制电子电流的新方法。在这里，我们使用单周期太赫兹瞬态来证明对纳米尖端光电子发射的广泛控制。太赫兹近场显示增强或抑制光电流，尖端作为一个超快整流二极管(6)。我们记录了相位分辨亚周期动力学，发现了太赫兹近场内电子传播引起的光谱压缩和膨胀。这些相互作用产生了丰富的光谱时间特征，并为成像和衍射提供了前所未有的超短自由电子脉冲控制。
The active control of matter by strong electromagnetic fields is of growing importance, with applications all across the optical spectrum from the extreme-ultraviolet to the far-infrared. In recent years, phase-stable terahertz fields have shown tremendous potential for observing and manipulating elementary excitations in solids(1-3). In the gas phase, on the other hand, driving free charges with terahertz transients provides insight into ultrafast ionization dynamics(4,5). Developing such approaches for locally enhanced terahertz fields in nanostructures will create new means to govern electron currents on the nanoscale. Here, we use single-cycle terahertz transients to demonstrate extensive control over nanotip photoelectron emission. The terahertz near-field is shown to either enhance or suppress photocurrents, with the tip acting as an ultrafast rectifying diode(6). We record phase-resolved sub-cycle dynamics and find spectral compression and expansion arising from electron propagation within the terahertz near-field. These interactions produce rich spectro-temporal features and offer unprecedented control over ultrashort free electron pulses for imaging and diffraction.