Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 20: Poster IA (Ultrafast phenomena; Optical properties; Transport; Theory)
HL 20.4: Poster
Montag, 16. März 2015, 15:00–20:00, Poster B
Ultrafast carrier dynamics and coherent oscillations in PbTe — •Prashant Padmanabhan1, Kestutis Budzinauskas1, Kiran H. Prabhakara1, Benoît Fauqué2, Kamran Behnia2, and Paul H. M. van Loosdrecht1 — 1Physics Institute 2, University of Cologne, 50937 Cologne, Germany — 2LPEM (UPMC-CNRS), Ecole Supérieure de Physique et de Chimie Industrielles, 75005 Paris, France
PbTe is a leading thermoelectric material that, in addition to its low thermal conductivity, shows unusually large carrier mobilities at very low doping levels. Here, we report on ultrafast pump-probe experiments on PbTe that shed light on these, as of yet, ill-understood properties. By employing time-resolved differential reflectivity measurements, the dynamics of electron-electron and electron-phonon interactions on the femtosecond time-scale are studied. The influences of sample temperature and pump fluence on the time constants of the various scattering pathways are also investigated. In addition, our experiments have revealed the presence of coherent oscillations in the differential reflectivity with a frequency close to those associated with LA+TO excitations; these may provide a means to further study the giant anharmonic coupling that is central to the low thermal conductivity of PbTe.