近日，德国埃尔朗根-纽伦堡大学(FAU)的Peter Hommelhoff课题组与德国罗斯托克大学的Thomas Fennel等人合作，并取得一项新成果。经过不懈努力，他们发现了追踪纳米金属尖端的阿秒电子发射。相关研究成果已于2023年4月26日在国际权威学术期刊《自然》上发表。

该研究团队通过背向散射电子的双色调制光谱学展示了如何揭示纳米结构中亚光学周期强场发射动力学，实现了阿秒精度。他们的实验中，测量了从锋利金属尖端发射的光电子能谱，作为两个颜色之间相对相位的函数。通过将时间相关的薛定谔方程的解投影到经典轨迹上，将光谱中相位依赖的特征与发射动力学相关联，并通过将量子模型与实验匹配，得出了710±30阿秒的发射持续时间。该研究结果为固体和其他系统的强场光电发射提供了定量的时间控制和精确的主动控制的机会，并对超快电子源、量子简并研究、亚泊松电子束、纳米等离子体学和皮赫兹电子学等多个领域产生了直接影响。

据悉，固体物质在强电场下会通过隧道效应释放电子。这个基本的量子过程是各种应用的核心，涵盖从直流运行中的高亮度电子源到激光驱动运行中的皮赫兹真空电子学等各种应用领域。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学。在气相中，亚周期电子动力学已经以数十阿秒的惊人精度被确定，但是迄今为止，在固体中，包括发射时间窗口的量子动力学仍未被测量。

附：英文原文

Title: Tracing attosecond electron emission from a nanometric metal tip

Author: Dienstbier, Philip, Seiffert, Lennart, Paschen, Timo, Liehl, Andreas, Leitenstorfer, Alfred, Fennel, Thomas, Hommelhoff, Peter

Issue&Volume: 2023-04-26

Abstract: 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 d.c. operation^1,2 to petahertz vacuum electronics in laser-driven operation^3,4,5,6,7,8. In the latter process, the electron wavepacket undergoes semiclassical dynamics^9,10 in the strong oscillating laser field, similar to strong-field and attosecond physics in the gas phase^11,12. There, the subcycle electron dynamics has been determined with a stunning precision of tens of attoseconds^13,14,15, 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 electrons¹⁶ uncovers the suboptical-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 Schrdinger equation onto classical trajectories relates phase-dependent signatures in the spectra to the emission dynamics and yields an emission duration of 710±30 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 from solid state and other systems and have direct ramifications for diverse fields such as ultrafast electron sources¹⁷, quantum degeneracy studies and sub-Poissonian electron beams^18,19,20,21, nanoplasmonics²² and petahertz electronics²³.

DOI: 10.1038/s41586-023-05839-6

Source: https://www.nature.com/articles/s41586-023-05839-6