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TT: Fachverband Tiefe Temperaturen
TT 68: Superconductivity: Fe-based Superconductors - Theory I
TT 68.4: Vortrag
Mittwoch, 2. April 2014, 16:00–16:15, HSZ 201
Electronic structure modification and ultrafast SDW generation due to coherent oscillation of the A1g phonon mode in BaFe2As2 — •Bhaskar Kamble and Ilya Eremin — Institut für Theoretische Physik III, Ruhr Universität Bochum, 44801 Bochum, Germany
Time-resolved ARPES experiments on BaFe2As2 demonstrate an in-phase oscillation of the ARPES spectral function at the Γ and M points [1], while time-resolved (tr) optical conductivity measurements on normal BaFe2As2 detect a periodic Spin Density Wave (SDW) at ultrafast time scales [2]. The period of oscillation in both cases equals the A1g phonon frequency in which the As atoms oscillate perpendicular to the Fe-planes. With a 5-orbital tight-binding (TB) model with the TB parameters dependent on the As-Fe-Fe angle α, and assuming that the electrons react adiabatically to the α oscillation in the A1g phonon, our calculations for changes in the electronic spectral function match well with tr-ARPES results if (i) α oscillates around a value slightly greater than its equilibrium value, and (ii) the electronic spectral function in the photoexcited state is calculated at a temperature higher than in the absence of the laser pulse. The mean-field magnetic order parameter for the (π,0) SDW state shows that the magnetization increases with α. This, coupled with the enhanced mean-α value in the photo-induced A1g phonon, offers a simple explanation for the ultrafast SDW-generation observed in normal BaFe2As2.
L. Rettig, Ph.D. thesis (Freie-Universität Berlin) (2012)
K. W. Kim et al., Nature Mat. 11, 497 (2012)