Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 42: Superconductivity: Fabrication, Properties, Electronic Structure

TT 42.4: Talk

Thursday, March 29, 2012, 15:45–16:00, H 3005

Ultrafast Phonon Hardening in Copper after Femtosecond Laser Excitation — •Fairoja Cheenicode Kabeer, Eeuwe S. Zijlstra, and Martin E. Garcia — Theoretical Physics, University Kassel, Heinrich-Plett-Str. 40, Kassel, Germany

When a femtosecond laser pulse interacts with a material it produces hot electrons, which can lead to changes in the interatomic potential. As a consequence, the lattice becomes unstable and forces appear on the atoms, driving many interesting ultrafast structural phenomena involving lattice vibrations. In this work we compute the dynamical matrix of copper before and after femtosecond laser excitation. For all phonon modes we find hardening as a function of the electronic temperature in the laser-excited state, which is opposite to the behavior of most materials, which soften when electrons are excited. We use this finding to study the possibility to squeeze the lattice vibrations in copper at low temperatures below the zero point motion.