Regensburg 2019 – wissenschaftliches Programm
O 95.3: Vortrag
Freitag, 5. April 2019, 11:00–11:15, H14
Excited state mapping and ultrafast population dynamics in In/Si(111) nanowires probed by trARPES — •Chris W. Nicholson1, Michele Puppin1, Andreas Lücke2, Wolf Gero Schmitt2, Laurenz Rettig1, Ralph Ernstorfer1, and Martin Wolf1 — 1Fritz Haber Institute, Berlin — 2University of Paderborn
Ultrafast electronic structure probes allow detailed insights into the microscopic processes underlying photo-induced phase transitions, as recently exemplified by the time- and angle-resolved photoemission spectroscopy (trARPES) study of the model (8x2) to (4x1) structural transition in In/Si(111) nanowires .
In this talk, I will address two further aspects of the electronic structure dynamics as probed by our trARPES setup utilizing a 22 eV laser at 500 kHz. The first is the extension of the band-mapping concept to states above the Fermi level, which allows a rigorous benchmarking of band structure calculations in this system. The second is an energy and momentum resolved analysis of the population dynamics during the phase transition. A comparison with a simulated band structure based on a transient electronic temperature finds impressive agreement, supporting the high electronic temperature extracted in the surface layer following excitation. These results are compared to those obtained with femtosecond electron diffraction  and imply a non-thermal phonon population of the surface In atoms and suggest a bottleneck for cooling of optical phonons.
 Nicholson et al. Science 362, 821 (2018)
 Frigge et al. Struct. Dyn. 5, 025101 (2018)