國立政治大學應用物理所

演講時間：113年1月3日(三)13:30
演講地點：志希樓2F 理學院會議室

摘要：

Photoelectron spectroscopy is a general tool to study the electronic structure of materials. Starting from the earlier development for gases and molecules, the energy and momentum analyses of photoelectrons have been providing rich information about the electronic states which can be directly compared with quantum mechanical calculations [1]. As a significant extension of the conventional experiments using synchrotron radiation or gas ionization lamps, there has been tremendous progress with laser-based photoelectron spectroscopy. By using femtosecond laser pulses as a light source, not only the electronic band structure can be explored but also their dynamics [2,3].

In this talk, electron dynamics in solids as well as photoelectron spectroscopy at surfaces will be introduced. As examples, two-photon photoemission (2PPE) and double photoemission (DPE) experiments will be described. In the 2PPE experiments, two times of the photon energy of the incident laser pulses will be absorbed by one single electron, and information from an originally unoccupied electronic state can be retrieved [4]. In the DPE experiments, two electrons are emitted upon the absorption of one single photon [5]. As a result, the distribution of these electron pairs can be fully characterized in the two-dimensional energy spectrum, providing valuable information about the interaction between electrons in solids [6]. Recent developments in our laboratory will be summarized at the end of the talk.

[1] S. Hüfner, Photoelectron Spectroscopy: principles and Applications, Springer (2003),
https://doi.org/10.1007/978-3-662-09280-4 .
[2] R. Haight, Surf. Sci. Rep. 21, 275 (1995).
[3] H. Petek and S. Ogawa, Prof. Surf. Sci. 56, 239 (1997).
[4] C.-T. Chiang et al., Phys. Rev. Lett. 103, 077601 (2009).
[5] J. Berakdar, Phys. Rev. B 58, 9808 (1998).
[6] A. Trützschler et al., Phys. Rev. Lett. 118, 136401 (2017).

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