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The advent of LaO1-xFxFeAs with Tc=26 K [1] has brought enormous interest to the high-Tc superconductor community. So far, four prototypes of crystal structures have been found in this Fe-pnictide family. These show a structural deformation related magnetic transition from a high temperature paramagnetic conductor to a low temperature anti-ferromagnetic metal at a transition temperature TN, different for each prototype. Charge carrier doping or isovalent substitution of the parent compound suppresses the AFM order and leads to a superconducting phase.
It is most important to study the electronic structure of these new superconductors, i.e., Fermi surfaces and band dispersions near the Fermi level at high symmetry points in order to obtain microscopic understanding of superconductivity. We have studied the electronic structure of Fe based 122 type parent compounds and their superconducting derivatives to reveal the important information on the Fermi surface nesting conditions (between hole pockets at the Brillouin zone center and electron pockets at zone corner) as a function of electron, hole doping, and isovalent substitution of P at As site in Ba(Eu)Fe2As2[2-4]. In particular, we studied in-plane and out-of-plane (with respect to the FeAs layer) band dispersions and Fermi surfaces. Our findings show that electron doping into parent BaFe2As2 destroy the nesting conditions and superconductivity emerges, accompanied by increase in the dimensionality of electronic structure [3]. We studied the photon energy dependent electronic structure along the zone center and the zone corner to reveal the dimensionality as a function of doping. We observe that charge carrier doping into parent compounds show a rigid-band-like behavior of electronic structure where as isovalent substitution show a non rigid-band-type nature. [1]. Y. Kamihara, T. Watanabe, M. Hirano, and H. Hosono, J. Am. Chem. Soc. 130, 3296 (2008). [2]. J. Fink, S. Thirupathaiah, et al., PRB, 79, 155118 [3]. S. Thirupathaiah, S. de Jong, et al., PRB, 81,104512 [4]. S. Thirupathaiah, E.D.L. Rienks, et al., arXiv: 1007.5205 Authors and affiliations: S. Thirupathaiah[1], E.D.L. Rienks[1], R. Ovsyannikov[1],Y. Huang[2], R. Huisman[2], E. Slooten[2], J. Kaas[2], E. van Heumen[2], S. de Jong[3], H.A. Duerr[1,3],Yu-Zhong Zhang[4], H.O. Jeschke[4], R. Valenti[4], A. Erb[5], R. Follath[1], H.S. Jeevan[6], P. Gegenwart[6], M.S. Golden[2], J. Fink[1,7] [1]. Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, 12489 Berlin, Germany [2]. Van der Waals-Zeeman Institute,University of Amsterdam, NL-1018 XE Amsterdam, The Netherlands [3]. Pulse Institute and Stanford Institute for Energy and Materials Science, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA [4]. Inst. für Theor. Physik, Goethe-Universität, Max-von-Laue-Strasse 1, 60438 Frankfurt, Germany [5]. Walther-Meissner-Institut, Walther-Meissner Strasse 8, 85748 Garching, Germany [6]. I. Physikalisches Institut, Georg-August- universität-Göttingen, 37077 Göttingen, Germany [7]. Leibniz-Institute for Solid State and Materials Research Dresden, P.O.Box 270116, D-01171 Dresden, Germany |
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