Discovery, Evidence and Properties for Superconducting Fe-Based Compounds Superconducting (A <sub>1− x</sub> Sr <sub>x</sub>) Fe <sub>2</sub> As <sub>2</sub> with A= K and Cs with T<sub>c</sub> up to 37 K.
POSTER
Abstract
In superconductivity (SC) discovery also understanding provide principal archetype, recently in 2008 discovery of iron-pnictide with several families, including spontaneous gauge symmetry breaking and Anderson-Higgs mechanism remain outstanding issue and opened new avenue of research in condensed matter physics. Tc raised in excess of 55ºK, bringing insights into bad-metal behavior, magnetism, and their striking interplay with unconventional SC. New high-Tc Fe-based-122 compounds, AFe2As2 with A = K, Cs, K/Sr, and Cs/Sr, were synthesized. Tc of KFe2As2 and CsFe2As2 is 3.8K and 2.6 K, respectively, Tc rises with partial substitution of Sr for K and Cs, Tc peaks at 37 K for 50%–60% Sr substitution, and compounds enter a spin-density-wave state with increasing electron number (Sr content). Compounds represent p-type analogs of the n-doped rare-earth oxypnictide SC. In cuprates correlations Hubbard-dominated, Fe-Pn involves multiorbital (multiband) physics and correlation effects. Electronic and structural behavior demonstrate the crucial role of (Fe2As2) layers in SC of Fe-based layered systems, and special feature of having elemental A layers provides new avenues to SC at higher Tc. Developments and intense activity ensued commonalities and differences between high-Tc Fe-based and Cuprate, Heavy-fermion and Organic SC. And I will discuss fundamental issues, such as symmetry of SC state, pairing mechanism, magnetic properties, electronic correlations, and role of orbital degrees of freedom.
*This work is supported in part by the T.L.L. Temple Foundation, the J.J. and R. Moores Endowment, the State of Texas through TCSUH, the USAF Office of Scientific Research, and the LBNL through the U.S. DOE; A.M.G. and B.L. acknowledge the support from the NSF (CHE0616805) and the R.A. Welch Foundation; We also thank Zhongjia Tang for help with crystallographic calculations.
Publication: Phys. Rev. Lett. 101, 107007
Presenters
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Kalyan Sasmal
- Department of Physics, University of California, San Diego.