标题： 从纳米金属尖端追踪阿秒电子发射 显示英文标题

标题： Tracing attosecond electron emission from a nanometric metal tip

摘要： 在强电场作用下的固体通过隧穿效应释放电子。这种基本的量子过程是各种应用的核心，从直流操作中的高亮度电子源到激光驱动操作中的拍赫兹真空电子学。在后一种过程中，电子波包在强振荡激光场中经历半经典动力学，类似于气相中的强场和阿秒物理。在那里，亚周期电子动力学已经以惊人的精度（几十阿秒）被确定，但在固体中，包括发射时间窗口在内的量子动力学迄今为止尚未被测量。在这里，我们展示了背散射电子的双色调制光谱揭示了纳米结构中的亚光学周期强场发射动力学，具有阿秒级的精度。在我们的实验中，测量了从尖锐金属针尖发射的光电子谱作为两种颜色相对相位的函数。将时间依赖的薛定谔方程的解投影到经典轨迹上，将光谱中的相位依赖特征与发射动力学相关联，并通过将量子模型与实验匹配得出发射持续时间为$710\pm30$阿秒。我们的结果为固态和其他系统中强场光电发射的定量定时和精确主动控制打开了大门，并对超快电子源、量子简并性研究和亚泊松电子束、纳米等离子学和拍赫兹电子学等多个领域有直接的影响。 显示英文摘要

摘要： Solids exposed to intense electric fields release electrons through tunnelling. This fundamental quantum process lies at the heart of various applications, ranging from high brightness electron sources in DC operation to petahertz vacuum electronics in laser-driven operation. In the latter process, the electron wavepacket undergoes semiclassical dynamics in the strong oscillating laser field, similar to strong-field and attosecond physics in the gas phase. There, the sub-cycle electron dynamics has been determined with a stunning precision of tens of attoseconds, but at solids the quantum dynamics including the emission time window has so far not been measured. Here we show that two-colour modulation spectroscopy of backscattering electrons uncovers the sub-optical-cycle strong-field emission dynamics from nanostructures, with attosecond precision. In our experiment, photoelectron spectra of electrons emitted from a sharp metallic tip are measured as function of the relative phase between the two colours. Projecting the solution of the time-dependent Schr\"odinger equation onto classical trajectories relates phase-dependent signatures in the spectra to the emission dynamics and yield an emission duration of $710\pm30$ attoseconds by matching the quantum model to the experiment. Our results open the door to the quantitative timing and precise active control of strong-field photoemission in solid state and other systems and have direct ramifications for diverse fields such as ultrafast electron sources, quantum degeneracy studies and sub-Poissonian electron beams, nanoplasmonics and petahertz electronics.