SKM 2023 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 48: Ultra-fast Phenomena
HL 48.3: Vortrag
Freitag, 31. März 2023, 10:00–10:15, POT 251
Transient Optical Property Changes in Semimetals with Strong Electron-Phonon Coupling — •Fabian Thiemann1, Germán Sciaini2, Alexander Kassen1, Tyler Lott2, and Michael Horn-von Hoegen1 — 1University of Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany — 2University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
Group V semimetals, such as bismuth used in this study, are well known for their strong electron-phonon coupling due to the inherent Peierls distortion of their lattice. In particular, the displacively excited coherent A1g phonon mode plays an important role in ultrafast studies on Bi. With knowledge of the excitation density we used a series of thin Bi films on Si(111) to reconstruct the transient dielectric function in an all optical pump-probe experiment. Though we only access the first half ps of dynamics, we separate the contributions from the excited carrier system and the coherent atomic motion. Our results suggest that we can describe the changes in optical properties caused by the non-equilibrium distribution of carriers still similar to a thermal dependency in equilibrium. In the regime of high excitation densities, we no longer can use the two-band Raman susceptibility approach to describe changes caused by the coherent phonons. We suggest that the light scattering is greatly enhanced by the excited carriers and that recently proposed band shifts in the time domain mainly define this part of changes of the dielectric function.