Journal article
Electronic origin of bond softening and hardening in femtosecond-laser-excited magnesium



Publication Details
Authors:
Grigoryan, N.; Zijlstra, E.; Garcia, M.
Publisher:
Institute of Physics (IoP) and Deutsche Physikalische Gesellschaft
Publication year:
2014
Journal:
New Journal of Physics
Pages range:
013002
Volume number:
16
Number of pages:
11
ISSN:
1367-2630

Abstract
Many ultrafast structural phenomena in solids at high fluences are related to the hardening or softening of particular lattice vibrations at lower fluences. In this paper we relate femtosecond-laser-induced phonon frequency changes to changes in the electronic density of states, which need to be evaluated only in the electronic ground state, following phonon displacement patterns. We illustrate this relationship for a particular lattice vibration of magnesium, for which we-surprisingly-find that there is both softening and hardening as a function of the femtosecond-laser fluence. Using our theory, we explain these behaviours as arising from Van Hove singularities: We show that at low excitation densities Van Hove singularities near the Fermi level dominate the change of the phonon frequency while at higher excitations Van Hove singularities that are further away in energy also become important. We expect that our theory can as well shed light on the effects of laser excitation of other materials.


Authors/Editors

Last updated on 2019-21-03 at 13:16

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