Evolution of quasiparticle excitations with enhanced electron correlations in superconducting AFe2As2 (A=K, Rb, and Cs)

Y. Mizukami, Y. Kawamoto, Y. Shimoyama, S. Kurata, H. Ikeda, T. Wolf, D. A. Zocco, K. Grube, H. v. Löhneysen, Y. Matsuda, and T. Shibauchi
Phys. Rev. B 94, 024508 – Published 13 July 2016

Abstract

In the heavily hole-doped iron-based superconductors AFe2As2 (A=K, Rb, and Cs), the electron effective mass increases rapidly with alkali-ion radius. To study the superconducting gap structure in this series, we measure the in-plane London penetration depth λab(T) in clean crystals of AFe2As2 down to low temperature T0.1 K. In KFe2As2, the superfluid stiffness ρsab(T)=λab2(0)/λab2(T) at low temperatures can be accounted for by the strongly band-dependent multiple gaps reported recently. Although the λab(T) in all systems exhibits similar nonexponential temperature dependence indicating nodes or small minima in the gap, we find that the quasiparticle excitations at low temperatures show a systematic suppression with increasing alkali-ion radius. A possible origin of such evolution of low-energy excitations is discussed in terms of the momentum-dependent effect of enhanced quasiparticle mass near a quantum critical point.

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  • Received 9 October 2015
  • Revised 12 June 2016

DOI:https://doi.org/10.1103/PhysRevB.94.024508

©2016 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Y. Mizukami1, Y. Kawamoto2, Y. Shimoyama2, S. Kurata1,2, H. Ikeda3, T. Wolf4, D. A. Zocco4, K. Grube4, H. v. Löhneysen4, Y. Matsuda2, and T. Shibauchi1

  • 1Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
  • 2Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
  • 3Department of Physical Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan
  • 4Institute of Solid State Physics (IFP), Karlsruhe Institute of Technology, D-76021 Karlsruhe, Germany

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Vol. 94, Iss. 2 — 1 July 2016

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