Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 43: Poster Session: Quantum Dots and Wires - Preparation and Characterization / Devices (incl. Laser) / Ultrafast Phenomena

HL 43.28: Poster

Dienstag, 27. März 2012, 09:30–12:30, Poster D

Laser-induced nonthermal melting in Si — •Tobias Zier, Eeuwe S. Zijlstra, and Martin E. Garcia — Theoretical Physics, University of Kassel, Germany

When a solid is excited by an intense ultrashort laser pulse a nonequilibrium state is created, where the electrons are very hot (several 10,000 K) and the ions remain cold. In silicon bond softening occurs after such an excitation. If the intensitiy of the laser pulse is high enough, some phonon modes become unstable. This causes ionic motion and a disordering within the first picosecond. This phenomenon is known as nonthermal (ultrafast) melting and has been studied intensively for different materials since the invention of ultrashort laser pulses. Recently, a new effect in this context was observed: the concerted decay of several x-ray diffraction peak intensities. To understand this new phenomenon we did some MD-simulations and calculated the structure-factors for every timestep after the excitation. With this information we were able to calculate the time-evolution of the x-ray diffraction peak intensities.