Dresden 2011 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 32: SC: Fe-based Superconductors - Theory
TT 32.2: Talk
Wednesday, March 16, 2011, 10:45–11:00, HSZ 304
Effect of Impurities and Effect of Ellipticity on the Spin Resonance in Iron-Based Superconductors — •Johannes Knolle1, Saurabh Maiti2, Ilya Eremin3, Andrey Chubukov2, and Mike Norman4 — 1Max-Planck-Institut fur Physik komplexer Systeme, D-01187 Dresden, Germany — 2Department of Physics, University of Wisconsin-Madison, Madison,Wisconsin 53706, USA — 3Institut fur Theoretische Physik III, Ruhr-Universitat Bochum, D-44801 Bochum, Germany — 4Materials Science Division, Argonne National Laboratory, Argonne, IL 60439-4845, USA
Iron-based superconductors are believed to have an unconventional order parameter with s± symmetry. Due to the sign change of the superconducting gap a spin resonance develops below the superconducting transition temperature. Based on an effective four-band model we analyze the doping dependence of this spin resonance and its sensitivity to non-magnetic, as well as, magnetic impurities. For zero ellipticity of the electron pockets the resonance becomes incommensurate at a critical doping δc, and, overall, the dispersion forms a so-called X-shape. For finite ellipticity, є, the resonance splits into two incommensurate peaks and δc increases with increasing є.
Both non-magnetic and magnetic impurities broaden the resonance. Its position depends on the interplay between the two impurity kinds and their intra- and inter-band scattering components. We find that the ratio between ωres/Tc increases with the strength of the inter-band impurity scattering which is consistent with available experimental data.