The availability of single attosecond (as) XUV pulses allows investigating ultrafast electron dynamics on the as time scale by recording slight temporal shifts of the photoelectron streaking in a simultaneously present strong IR field. The physical origin of the observed small delays is not yet understood and controversial theoretical models coexist demonstrating our still limited understanding of the fundamentals of the photoemission process. Here we report our progress to model and interpret photoemission delays measured using as-time-resolved photoemission from the layered crystals WSe2 and the non-centrosymmetric BiTeCl. Quantum mechanical modelling on the single particle level and classical trajectory calculations yield no satisfactory explanation of the observed relative delays between photoemission events from different initial states. Local atomic effects and many body corrections occurring inside the atom from which the electron is emitted yield significant corrections to the total photoemission delay and improve the match between experimental observation and theoretical prediction. This sheds new light on the fundamental mechanism involved in the photoemission process and shows that a refined model of photoemission that accounts for these local effets is needed.
Walter Pfeiffer, "Modelling and physical interpretation of time-delay differences observed in attosecond-time-resolved photoemission from WSe2 and BiTeCl surfaces (Conference Presentation)," Proc. SPIE 10102, Ultrafast Phenomena and Nanophotonics XXI, 101020G (Presented at SPIE OPTO: January 31, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2255639.5391450798001.
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