SKM 2023 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 6: Poster

KFM 6.14: Poster

Dienstag, 28. März 2023, 17:00–19:00, P3

Material dependent differences in spectroscopic changes of the transient reflectivity on ultrashort timescales — Jonathan Frank, Julian Mertens, Felix Hoff, and •Matthias Wuttig — 1. Institute of Physics (IA), RWTH Aachen University, Aachen, Germany

Optical spectroscopy is a well-established technique to characterize solids. It can be utilized to distinguish different types of chemical bonding, i.e. separate solids which employ metallic, ionic and covalent bonding. We have tried to understand if these differences in bonding are still visible if the materials are excited with femto-second laser pulses. Femtosecond pump-probe spectroscopy experiments at a fixed pump-pulse wavelength were carried out in an isotropic detection scheme, to investigate the wavelength dependent reflectivity changes of optically excited samples on sub-ps timescales for wavelengths ranging from the visible to the near infrared. The measurements were carried out on various pure metals, chiral topological semimetals and semiconductors. The reflectivity changes, for a given material, vary greatly in duration and magnitude, depending on the probe wavelength. Furthermore, while an initial decrease in the transient reflectivity may be observed at one probe wavelength, an increase may be measured with another. This behavior is intrinsically linked to the excitation of carriers, their subsequent relaxation and their interaction with the lattice. The results for different materials are presented and compared, and trends within a material group evaluated. A possible link to emergent properties, conductivity and dielectric function, is discussed.