Ultrafast structural dynamics of the Fe-pnictide parent compound BaFe(2)As(2).
Using femtosecond time-resolved x-ray diffraction we investigate the structural dynamics of the coherently excited A(1g) phonon mode in the Fe-pnictide parent compound BaFe(2)As(2). The fluence dependent intensity oscillations of two specific Bragg reflections with distinctly different sensitivity to the pnictogen height in the compound allow us to quantify the coherent modifications of the Fe-As tetrahedra, indicating a transient increase of the Fe magnetic moments. By a comparison with time-resolved photoemission data, we derive the electron-phonon deformation potential for this particular mode. The value of Δμ/Δz=-(1.0-1.5)  eV/Å is comparable with theoretical predictions and demonstrates the importance of this degree of freedom for the electron-phonon coupling in the Fe pnictides.
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
L
L
Rettig
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
S O
SO
Mariager
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and Institute for Quantum Electronics, Physics Department, ETH Zürich, CH-8093 Zürich, Switzerland.
A
A
Ferrer
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
S
S
Grübel
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
J A
JA
Johnson
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and Ecole Polytechnique Fédérale de Lausanne, Laboratoire de Spectroscopie Ultrarapide, ISIC, FSB, CH-1015 Lausanne, Switzerland.
J
J
Rittmann
Karlsruhe Institute of Technology, Institut für Festkörperphysik, D-76021 Karlsruhe, Germany.
T
T
Wolf
Institute for Quantum Electronics, Physics Department, ETH Zürich, CH-8093 Zürich, Switzerland.
S L
SL
Johnson
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
G
G
Ingold
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland and SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
P
P
Beaud
Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
U
U
Staub