title: Interaction-induced singular Fermi surface in a high-temperature oxypnictide superconductor.
abstract: In the family of iron-based superconductors, LaFeAsO-type materials possess the simplest electronic structure due to their pronounced two-dimensionality. And yet they host superconductivity with the highest transition temperature Tc ≈ 55K. Early theoretical predictions of their electronic structure revealed multiple large circular portions of the Fermi surface with a very good geometrical overlap (nesting), believed to enhance the pairing interaction and thus superconductivity. The prevalence of such large circular features in the Fermi surface has since been associated with many other iron-based compounds and has grown to be generally accepted in the field. In this work we show that a prototypical compound of the 1111-type, SmFe(0.92)Co(0.08)AsO , is at odds with this description and possesses a distinctly different Fermi surface, which consists of two singular constructs formed by the edges of several bands, pulled to the Fermi level from the depths of the theoretically predicted band structure by strong electronic interactions. Such singularities dramatically affect the low-energy electronic properties of the material, including superconductivity. We further argue that occurrence of these singularities correlates with the maximum superconducting transition temperature attainable in each material class over the entire family of iron-based superconductors.
authors.affiliation: 1] Leibniz Institute for Solid State and Materials Research, IFW, 01069 Dresden, Germany [2] Physics Department, University of California-San Diego,La Jolla, CA 92093, USA.
authors.forename: A
authors.initials: A
authors.lastname: Charnukha
authors.affiliation: 1] Leibniz Institute for Solid State and Materials Research, IFW, 01069 Dresden, Germany [2] Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore-560 012, India.
authors.forename: S
authors.initials: S
authors.lastname: Thirupathaiah
authors.affiliation: 1] Leibniz Institute for Solid State and Materials Research, IFW, 01069 Dresden, Germany [2] Physikalisches Institut und Röntgen Center for Complex Materials Systems, Universität Würzburg, 97074 Würzburg, Germany.
authors.forename: V B
authors.initials: VB
authors.lastname: Zabolotnyy
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW, 01069 Dresden, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Büchner
authors.affiliation: Laboratory for Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: N D
authors.initials: ND
authors.lastname: Zhigadlo
authors.affiliation: Laboratory for Solid State Physics, ETH Zurich, CH-8093 Zurich, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Batlogg
authors.affiliation: Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany.
authors.forename: A N
authors.initials: AN
authors.lastname: Yaresko
authors.affiliation: Leibniz Institute for Solid State and Materials Research, IFW, 01069 Dresden, Germany.
authors.forename: S V
authors.initials: SV
authors.lastname: Borisenko