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TT: Fachverband Tiefe Temperaturen

TT 36: Superconductivity: Fe-based Superconductors - Fe(Se,Te), LiFeAs, and other Materials

TT 36.1: Vortrag

Mittwoch, 13. März 2013, 09:30–09:45, H18

Interplay between lattice and spin degrees of freedom in FeSe superconductors — Vladimir Gnezdilov¹, •Peter Lemmens², Yurii Pashkevich³, Tatiana Shevtsova³, Alexander Gusev³, Dirk Wulferding², Dmitriy Chareev⁴, and Alexander Vasiliev⁵ — ¹ILTPE, Kharkov, Ukraine — ²IPKM, TU-BS, Braunschweig — ³DonFTI, Donetsk, Ukraine — ⁴IEM, RAS, Moscow, Russia — ⁵Moscow State Univ., Moscow, Russia

Recently grown high quality FeSe single crystals show pronounced anomalies in the temperature dependent Raman spectra. An anomalous hardening of one phonon mode upon decreasing temperature is related to local fluctuations of the Fe orbital occupation, described by the Fe spin state. The enhancement of the low-frequency spectral weight above the structural phase transition temperature T_S and its change below T_S is discussed in connection with the opening of a spin state gap which results in the absence of magnetic order in FeSe. Work supported by DFG, B-IGSM and NTH School for Contacts in Nanosystems.