Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 119: Non-Equilibrium Daynamics in Light-Driven Materials: Theory Meets Experiment
O 119.6: Talk
Friday, March 16, 2018, 12:45–13:00, MA 141
Ultrafast dynamics of bands and bonds in In/Si(111) nanowires probed by trARPES at 500 kHz — •Chris W. Nicholson1, Andreas Lücke2, Wolf Gero Schmidt2, Michele Puppin1, Laurenz Rettig1, Ralph Ernstorfer1, and Martin Wolf1 — 1Fritz-Haber-Institut, Berlin, Germany — 2Universität Paderborn, Germany
In a Born-Oppenheimer description, nuclear dynamics evolve across a free energy surface determined by the occupation of electronic states as a function of nuclear coordinates. Ultrafast photo-induced phase transitions (PIPTs) provide a test case for how the forces and resulting nuclear motion along the reaction coordinate originate from a non-equilibrium population of excited electronic states.
Utilizing femtosecond time and angle resolved photoemission spectroscopy (trARPES) with a novel 500 kHz XUV laser source, we obtain direct access to the transient electronic structure during an ultrafast PIPT in a model system: the structural transition in In/Si(111) nanowires. A detailed reaction pathway is laid out, including temporally separated electronic and structural phase transitions. Comparison with ab initio molecular dynamics simulations reveals the crucial role played by localized photo-holes in shaping the potential energy landscape. Our detailed insights enable a combined momentum and real space description of ultrafast PIPTs including the ultrafast formation of chemical bonds [1].
[1] Nicholson et al. Submitted (2017)