Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 52: Superconductivity: Fe-based Superconductors – FeSe and others
TT 52.10: Talk
Wednesday, March 18, 2015, 12:00–12:15, H 2053
Pseudogap from preformed Cooper pairs in a platinum-iron-arsenide superconductor — M. A. Surmach1, F. Brückner1, S. Kamusella1, R. Sarkar1, P. Y. Portnichenko1, J. T. Park2, H. Luetkens3, P. Biswas3, W. J. Choi4, Y. I. Seo4, Y. S. Kwon4, H.-H. Klauss1, and •D. S. Inosov1 — 1TU Dresden, Germany — 2MLZ, Garching, Germany — 3PSI, Villigen, Switzerland — 4DGIST, Daegu, Republic of Korea
Using a combination of µSR, INS and NMR, we investigated the novel iron-based superconductor with a triclinic crystal structure (CaFe1−xPtxAs)10Pt3As8 (Tc=13 K). The T-dependence of the superfluid density from our µSR relaxation-rate measurements indicates the presence of two superconducting gaps. According to our INS measurements, commensurate spin fluctuations are centered at the (π, 0) wave vector. Their intensity is unchanged across Tc, indicating the absence of a spin resonance typical for many Fe-based superconductors. Instead, we observed a peak in the spin-excitation spectrum around ω0=7 meV at the same wave vector, which persists above Tc. The temperature dependence of magnetic intensity at 7 meV revealed an anomaly around T∗=45 K related to the disappearance of this new mode. A suppression of the spin-lattice relaxation rate, 1/T1T, observed by NMR immediately below T∗ without any notable subsequent anomaly at Tc, indicates that T∗ could mark the onset of a pseudogap in (CaFe1−xPtxAs)10Pt3As8, which is likely associated with the emergence of preformed Cooper pairs.