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TT: Fachverband Tiefe Temperaturen

TT 45: Superconductivity: Fe-based Superconductors - 1111,111, FeSe

TT 45.8: Vortrag

Dienstag, 1. April 2014, 15:45–16:00, HSZ 201

Orbital-selective metal-insulator transition and gap formation above T_c in superconducting Rb_1−x Fe_2−ySe₂ — •Zhe Wang¹, Michael Schmidt¹, Jonas Fischer¹, Vladimir Tsurkan¹, Markus Greger², Dieter Vollhardt², Alois Loidl¹, and Joachim Deisenhofer¹ — ¹Experimentalphysics 5, Univ. Augsburg, Germany — ²Theoreticalphysics 3, Univ. Augsburg, Germany

We report on a hierarchy of temperatures T_c < T_gap < T_met in superconducting Rb_1−x Fe_2−ySe₂ observed by THz spectroscopy. Above T_met = 90 K the material reveals semiconducting characteristics. Below T_met a coherent metallic THz response emerges. This metal-to-insulator-type, orbital selective transition is indicated by an isosbestic point in the temperature dependence of the optical conductivity and dielectric constant at THz-frequencies. At T_gap = 61 K a gap opens in the THz regime and then the superconducting transition occurs at T_c = 32 K. This sequence of temperatures seems to reflect a corresponding hierarchy of the electronic correlations in the different bands.