Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 120: Ultra-fast phenomena II

HL 120.2: Vortrag

Freitag, 4. April 2014, 11:45–12:00, POT 006

Phonon hardening and softening in femtosecond-laser-excited metals — •Naira S. Grigoryan, Fairoja C. Kabeer, Eeuwe S. Zijlstra, and Martin E. Garcia — Theoretische Physik, Universität Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany

Many ultrafast structural phenomena in solids at high fluences are related to changes in the phonon frequencies at lower fluences. Here we studied the response of representative phonon modes of Mg and Cu to femtosecond-laser excitation using electronic-temperature-dependent density functional theory. We found softening of some and hardening of other lattice modes, where some modes even showed both behaviors as a function of the excitation strength. We relate the laser-induced changes in the phonon frequencies to changes in the ground-state electronic density of states following atomic displacement patterns in the directions of a phonon eigenmode. Using this relationship we established a general connection between the unexcited electronic structure of a material and the structural response to intense femtosecond-laser excitation.

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