Weak Superconducting Pairing and a Single Isotropic Energy Gap in Stoichiometric LiFeAs

D. S. Inosov, J. S. White, D. V. Evtushinsky, I. V. Morozov, A. Cameron, U. Stockert, V. B. Zabolotnyy, T. K. Kim, A. A. Kordyuk, S. V. Borisenko, E. M. Forgan, R. Klingeler, J. T. Park, S. Wurmehl, A. N. Vasiliev, G. Behr, C. D. Dewhurst, and V. Hinkov
Phys. Rev. Lett. 104, 187001 – Published 6 May 2010

Abstract

We report superconducting (SC) properties of stoichiometric LiFeAs (Tc=17K) studied by small-angle neutron scattering (SANS) and angle-resolved photoemission (ARPES). Although the vortex lattice exhibits no long-range order, well-defined SANS rocking curves indicate better ordering than in chemically doped 122 compounds. The London penetration depth λab(0)=210±20nm, determined from the magnetic field dependence of the form factor, is compared to that calculated from the ARPES band structure with no adjustable parameters. The temperature dependence of λab is best described by a single isotropic SC gap Δ0=3.0±0.2meV, which agrees with the ARPES value of Δ0ARPES=3.1±0.3meV and corresponds to the ratio 2Δ/kBTc=4.1±0.3, approaching the weak-coupling limit predicted by the BCS theory. This classifies LiFeAs as a weakly coupled single-gap superconductor.

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  • Received 20 February 2010

DOI:https://doi.org/10.1103/PhysRevLett.104.187001

©2010 American Physical Society

Authors & Affiliations

D. S. Inosov1,*, J. S. White2, D. V. Evtushinsky3, I. V. Morozov4,3, A. Cameron5, U. Stockert3, V. B. Zabolotnyy3, T. K. Kim3, A. A. Kordyuk3,6, S. V. Borisenko3, E. M. Forgan5, R. Klingeler3, J. T. Park1, S. Wurmehl3, A. N. Vasiliev4, G. Behr3, C. D. Dewhurst7, and V. Hinkov1

  • 1Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany
  • 2Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
  • 3Leibnitz Institute for Solid State Research, IFW Dresden, D-01171 Dresden, Germany
  • 4Moscow State University, Moscow 119991, Russia
  • 5School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
  • 6Institute for Metal Physics of the National Academy of Sciences of Ukraine, 03142 Kyiv, Ukraine
  • 7Institut Laue-Langevin, 6 Rue Jules Horowitz, F-38042 Grenoble, France

  • *Corresponding author. d.inosov@fkf.mpg.de

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Vol. 104, Iss. 18 — 7 May 2010

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