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Double photoemission on correlated electron pairs in solids using MHz high-order harmonics

Date: 2018-10-15
Time: 10:00
Venue: M253
Speaker: Dr. Cheng-Tien Chiang (江正天)

Institute of Physics, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany


     Recent development of high-order harmonic generation (HHG) using femtosecond lasers has allowed the applications of widely tunable vacuum-ultraviolet light sources to surface science. However, due to the low repetition rates of conventional high-power laser systems, the potential of HHG-based photoelectron spectroscopy and microscopy has been largely limited. In this talk, a newly developed, compact HHG light source working at megahertz repetition rates as well as its application to angle-resolved photoelectron spectroscopy (ARPES) will be introduced. Moreover, by combing this HHG light source with a pair of time-of-flight photoelectron spectrometers, a band-resolved analysis of correlated electron pairs in solids can be realized in double photoemission (DPE) experiments. In this talk, the signatures of two-electron states in the two-dimensional DPE spectra will be discussed in terms of electron-electron interaction. 


    Dr. Cheng-Tien Chiang, born in 1984 in Taipei, Taiwan, obtained his Bachelor and Maser degrees in the Department of Physics, National Taiwan University, Taipei (2005, 2007), and PhD in the Max Planck Institute of Microstructure Physics and the Martin-Luther-University Halle-Wittenberg in Halle (Saale), Germany (2011). His research focuses on the electronic structure at surfaces and interfaces of transition metals and their oxides. In these systems, the interaction between localized d electrons as well as the interplay between the d and sp electrons play dominant roles. To observe these effects directly in experiments, he uses laser-based photoelectron spectroscopy and microscopy with femtosecond time-resolution.