Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 35: Ultrafast Phenomena I

O 35.6: Talk

Tuesday, March 8, 2016, 10:45–11:00, H10

The role of intervalley scattering and phonon softening in the ultrafast carrier dynamics of PbTe — Prashant Padmanabhan, Kestutis Budzinauskas, Kiran H. Prabhakara, and •Paul H. M. van Loosdrecht — Physics Institute 2, University of Cologne, 50937 Cologne, Germany

PbTe is a leading thermoelectric material, notable for its low thermal conductivity and unusually large carrier mobility at very low doping levels. Here, we report on ultrafast pump-probe experiments on PbTe that shed light on the ultrafast relaxation of highly excited carriers. By employing time-resolved differential reflectivity measurements, we probe the dynamics of electron-electron and electron-phonon interactions on the femtosecond time-scale. Additionally, the use of a super-continuum probe pulse allows us to investigate the wavelength dependence of the carrier relaxation dynamics. Our results suggest that phonon mediated intervalley scattering involving the band gap between the Γ and K points plays a significant role in carrier cooling. Further, the temperature dependence of these dynamics point to anomalous behavior that may be the result of phonon softening, recently reported to be a key element in the unique thermal properties of PbTe.