Berlin 2012 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Superconductivity, Measuring Devices, Matter at Low Temperature: Poster Session
TT 33.6: Poster
Mittwoch, 28. März 2012, 15:00–19:00, Poster B
Coherent excitations and e-ph coupling in 122 FeAs compounds investigated by time-resolved ARPES — •I. Avigo1, R. Cortés2,3, L. Rettig1,2, S. Thirupathaiah4, H. S. Jeevan5, P. Gegenwart5, T. Wolf6, M. Ligges1, M. Wolf2,3, J. Fink4, and U. Bovensiepen1,2 — 1Universität Duisburg-Essen — 2Freie Universität Berlin — 3Fritz-Haber-Institut d. MPG, Berlin — 4IFW Dresden — 5Georg-August Universität Göttingen — 6Karlsruhe Institute of Technology
We investigate the coupling of low energy electrons to lattice vibrations in iron based high-Tc superconductors to shed light on the mechanisms leading to superconductivity. Femtosecond time and angle-resolved photoemission spectroscopy was employed to analyze the response of the electronic system of 122 iron pnictide compounds to optical excitation. Oscillations of the spectral weight around the Fermi level were observed showing three different coherently excited phonon modes. We identify the symmetric A1g mode at 5.6 THz, corresponding to the displacement of the As atoms perpendicular to the Fe-plane, and two further modes at 3.3 THz and 2.6 THz. Our observations are consistent with calculations predicting strong e-ph coupling for the A1g mode. By analyzing the rate of energy relaxation of excited electrons we estimate the moment-averaged e-ph coupling constant to λ<0.2 which makes simple e-ph interaction an unlikely pairing candidate for superconductivity. This work has been funded by the DFG through BO 1823/2 and SPP 1458. R.C. acknowledges the Alexander von Humboldt Foundation.