Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 40: Superconductivity: Ferropnictides 1
TT 40.15: Vortrag
Donnerstag, 26. März 2009, 18:00–18:15, HSZ 03
Renormalized in-plane plasma frequencies and insight into the superconductivity of iron pnictides from optical studies and low-temperature µSR data — •Stefan-Ludwig Drechsler1, Helge Rosner2, Klaus Koepernik1, Mandy Grobosch1, Guenter Behr1, Roman Schuster1, Friedrich Roth1, Saad Elgazzar3, Bernd Buechner1, and Martin Knupfer1 — 1IFW-Dresden, D-01171 Dresden, Germany — 2MPI-CPfS Dresden, Germany — 3Menoufia Univ., Shebin El-kom, Egypt & Uppsala Univ., Sweden
Theoretical values for the unscreened plasma frequencies of several Fe pnictides from DFT-LDA based calculations are compared with experimental plasma frequencies obtained from reflectivity measurements on both polycrystalline samples [1] and single crystals. The sizable renormalization observed for all considered compounds points to the presence of significant many-body effects beyond the LDA. From the measured large empirical background polarizabilities ε∞ ∼> 10-15 we discard a sizable value of the Coulomb repulsion U∼ 4 eV on Fe sites as proposed in the literature. From the extrapolated µSR (muon spin rotation) penetration depth data at very low-temperature and the experimental unscreened plasma frequency the total coupling constant λtot for the electron-boson interaction is estimated within the framework of the Eliashberg-theory within an effective single band approximation. For LaFeAsO0.9F0.1 a weak to intermediately strong coupling regime is found whereas in the pronounced multiband case a constraint for various intraband coupling constants is obtained.
[1] S.-L. Drechsler, M. Grobosch et al., PRL 101 in press (2008).