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TT: Fachverband Tiefe Temperaturen

TT 32: SC: Fe-based Superconductors - Theory

TT 32.2: Vortrag

Mittwoch, 16. März 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 δ_c, and, overall, the dispersion forms a so-called X-shape. For finite ellipticity, є, the resonance splits into two incommensurate peaks and δ_c 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 ω_res/T_c increases with the strength of the inter-band impurity scattering which is consistent with available experimental data.