Berlin 2015 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 43: Superconductivity: Fe-based Superconductors – 122
TT 43.6: Vortrag
Dienstag, 17. März 2015, 15:30–15:45, H 2053
Ultrafast structural dynamics of the Fe-pnictide parent compound BaFe2As2 — •L. Rettig1, S.O. Mariager1, A. Ferrer1,2, S. Grübel1, J.A. Johnson1, J. Rittmann1,3, T. Wolf4, S.L. Johnson2, G. Ingold1, P. Beaud1, and U. Staub1 — 1Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland — 2ETH Zürich, CH-8093 Zürich, Switzerland — 3EPFL, CH-1015 Lausanne, Switzerland — 4KIT, D-76021 Karlsruhe, Germany
Understanding the interplay of the various degrees of freedom such as the electrons, spins and lattice is essential for many complex materials, including the high-temperature superconductors. In the Fe pnictides, especially the strong sensitivity of the electronic and magnetic properties to the Fe-As tetrahedra angle plays a crucial role for superconductivity and demonstrates a strong magneto-structural coupling.
Here, we use femtosecond time-resolved x-ray diffraction to investigate the structural dynamics in the Fe-pnictide parent compound BaFe2As2. We observe fluence dependent intensity oscillations of two specific Bragg reflections. Their distinctly different sensitivity to the pnictogen height demonstrates the coherent excitation of the A1g phonon mode and allows us to quantify the coherent modifications of the Fe-As tetrahedra. By a comparison with time-resolved photoemission data we derive the electron-phonon deformation potential for this particular mode, which is comparable to theoretical predictions. Our results demonstrate the importance of this structural degree of freedom for the electron-phonon coupling in the Fe pnictides and indicate an ultrafast increase of the Fe magnetic moments.