Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 28: FS: Time-Resolved Spectroscopy in Correlated Electron Systems:
Experiment and Theory

TT 28.3: Talk

Thursday, March 25, 2010, 10:30–10:45, H18

Electron-phonon interaction in 122-iron pnictides investigated by femtosecond time-resolved ARPES. — •Rocío Cortés¹, L. Rettig¹, S. Thirupathaiah², U. Bovensiepen^1,3, M. Wolf¹, H. A. Dürr², P. Gegenwart⁴, T. Wolf⁵, and J. Fink^2,6 — ¹Freie Universität Berlin, D-14195 Berlin — ²Helmholtz-Zentrum Berlin, D-12489 Berlin — ³Universität Duisburg-Essen, D-47048 Duisburg — ⁴Georg-August-Universität Göttingen, D-37077 Göttingen — ⁵Karlsruhe Institute of Technology, D-76021 Karlsruhe — ⁶Leibniz-Institute for Solid State and Materials Research Dresden, D-01171 Dresden

The new class of FeAs based high-T_c superconductors exhibits a complex interplay between electronic, magnetic and lattice degrees of freedom. Here we report on electron-phonon coupling in EuFe₂As₂ and BaCo_0.15Fe_1.85As₂ investigated by femtosecond (fs) time- and angle-resolved photoelectron spectroscopy (trARPES). The samples were excited by 1.5 eV fs laser pulses, at 100 K equilibrium temperature. The temporal evolution of their electronic band structure after photoexcitation was probed by time-delayed 6 eV fs pulses. In this way a periodic oscillation of the electronic structure in the vicinity of the Fermi level was observed, which is attributed to coherent phonon modes and electron phonon-coupling. Comparison with Raman scattering results[1] allows to assign the mode with the highest frequency to the A_1g mode, which modifies the Fe-As distance and could be involved with the mechanism leading to superconductivity in these materials.

[1] A.P. Litvinchuk et al., Phys. Rev. B 78, 060503(R) (2008)