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Berlin 2012 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 23: Superconductivity: Fe-based Superconductors - Fe(Se/Te)

TT 23.1: Talk

Wednesday, March 28, 2012, 09:30–09:45, H 2053

Separation of iron spin states in chalcogenide superconductorsVladimir Gnezdilov1, •Peter Lemmens2, Yurii Pashkevich3, Alexander Gusev3, Tatiana Shevtsova3, Karina Lamonova3, Dirk Wulferding2, Ekaterina Pomjakushina4, and Kazimierz Conder41ILTPE NAS, Ukraine — 2IPKM, TU-BS, Braunschweig, Germany — 3DonFTI, Donetsk, Ukraine — 4PSI, Villigen, Switzerland

We present a Raman study of superconducting single crystals M1−xFe2−ySe2 (M = Rb, Cs). Our data together with ab-initio spin-polarized band structure and phonon calculations show the presence of two phases: an insulating vacancy ordered Rb2Fe4Se5 phase and a metallic phase with iron in a low spin state. At high frequencies we observe electronic d-d interband transitions, indicating the insulating state. Our results show that iron is in close proximity to a spin state instability. Work supported by DFG and Rus-Ukr.

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