Attosecond spectroscopy in condensed matter
Attosecond spectroscopy in condensed matter
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DOI：
10.1038/nature06229
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发表时间：
2007-10-25
期刊：
影响因子：
64.8
通讯作者：
Heinzmann, U.
中科院分区：
文献类型：
--
作者：
Cavalieri, A. L.;Mueller, N.;Heinzmann, U.
对凝聚态系统中电子动力学行为的全面了解与许多现代技术的发展有关，如半导体和分子电子学、光电子学、信息处理和光伏技术。然而，探测电子过程仍然具有挑战性，其中许多过程发生在阿秒(1 As=10(-18)S)区域。相比之下，原子运动发生在飞秒(1飞秒=10(-15)S)的时间尺度上，并已使用飞秒X射线源(3)在固体中实时绘制(1，2)。在这里，我们扩展了以前用于研究气体中孤立原子的阿秒技术(4，5)，以实时观察凝聚态系统中和表面上的电子运动。我们通过探测单晶钨的光电子发射，证明了我们有能力以阿秒分辨率获得电荷动力学的直接时间域访问。我们的数据显示，从金属的局域核态发出的光电子与从非局域导带态释放的光电子之间存在大约100阿秒的延迟。这些结果表明，阿秒计量学不仅是探索气相系统的有力工具，而且是探索凝聚态系统和表面上发生在阿秒时间尺度上的基本电子过程的有力工具。
Comprehensive knowledge of the dynamic behaviour of electrons in condensed-matter systems is pertinent to the development of many modern technologies, such as semiconductor and molecular electronics, optoelectronics, information processing and photo-voltaics. Yet it remains challenging to probe electronic processes, many of which take place in the attosecond (1 as = 10(-18) s) regime. In contrast, atomic motion occurs on the femtosecond (1 fs = 10(-15) s) timescale and has been mapped in solids in real time(1,2) using femtosecond X-ray sources(3). Here we extend the attosecond techniques(4,5) previously used to study isolated atoms in the gas phase to observe electron motion in condensed-matter systems and on surfaces in real time. We demonstrate our ability to obtain direct time-domain access to charge dynamics with attosecond resolution by probing photoelectron emission from single-crystal tungsten. Our data reveal a delay of approximately 100 attoseconds between the emission of photoelectrons that originate from localized core states of the metal, and those that are freed from delocalized conduction-band states. These results illustrate that attosecond metrology constitutes a powerful tool for exploring not only gas-phase systems, but also fundamental electronic processes occurring on the attosecond timescale in condensed-matter systems and on surfaces.