Transient Spin Density Wave Order Induced in the Normal State of BaFe2As2 by Coherent Lattice Oscillations
1 Department of Physics and Center for Applied Photonics, University of Konstanz, Universitätsstr. 10, 78464 Konstanz, Germany
2 University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Chemin du Musée 3, 1700 Fribourg, Switzerland
3 Department of Physics, Chungbuk National University, 52 Naesudong-ro, Cheongju 361-763, Korea
4 Department of Physics, University of Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany
5 Karlsruhe Institute of Technology, Institute for Solid State Physics, 76021 Karlsruhe, Germany
6 Complex Matter Department, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
We trace the ultrafast dynamics of the spin density wave gap of the pnictide system BaFe2As2 probing resonantly with broadband multi-terahertz pulses. The photoexcitation in the low-temperature ground state leads to a fast suppression of the spin order followed by a slower recovery process. Surprisingly, in the normal state, we observe periodic oscillations of the spin density wave feature at a frequency as high as 5.5 THz. Our results indicate a transient development of a macroscopic order driven by a coherent lattice oscillation and attest to a pronounced spin–phonon coupling in pnictides.
© Owned by the authors, published by EDP Sciences, 2013
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