AF-Spin fluctuations and its possible relation with the superconducting pairing mechanism and the superconducting energy gap symmetry of the stoichiometric iron-pnictide superconductor LiFeAs (Tc~18K).

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. Normal state AF-spin fluctuations and its possible relation with SC pairing mechanism and symmetry of SC energy gap function are important issue in iron-pnictide family of SC and are probed by lower critical field deduced from vortex penetration, specific heat measurements of SC single crystals and reversible magnetization of polycrystalline LiFeAs sample. LiFeAs seems to be almost isotropic and can be fit as a s-wave two-gap SC with the superfluid density strongly affected by the smaller gap. The specific heat of LiFeAs single crystals reveals s-multigap feature with a small gap of about 0.7 meV dominating low-temperature electronic quasiparticle excitations. A significant contribution from Einstein phonons is observed, as well as a noticeable residual linear term γ0. Also, I will discuss magnetic properties, Hc1 anisotropy, anisotropic gaps, electronic correlations, and the role of orbital degrees of freedom. Developments and intense activity ensued commonalities and differences between high-Tc Fe-based, Cuprate, Heavy-fermion and Organic SC.

*The work in Houston is supported in part by the U.S. Air Force Office of Scientific Research, the T. L. L. Temple Foundation, the John J. and Rebecca Moores Endowment, the Robert A. Welch Foundation under Grant No. E-1297, and the State of Texas through the Texas Center for Superconductivity at the University of Houston; and at Lawrence Berkeley Laboratory by the Director, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. A.M.G., B.L., and Z.T. acknowledge support from the NSF Grant No. CHE-0616805 and the R.A. Welch Foundation.

Publication: PHYSICAL REVIEW B 81, 144512 (2010); PHYSICAL REVIEW B 81, 134527 (2010)

Presenters

  • Kalyan Sasmal

    • Department of Physics, University of California, San Diego. TCSUH and Department of Physics, University of Houston.
    • Department of Physics, University of California, San Diego.

Authors

  • Kalyan Sasmal

    • Department of Physics, University of California, San Diego. TCSUH and Department of Physics, University of Houston.
    • Department of Physics, University of California, San Diego.

  • F Y Wei

    • TCSUH and Department of Physics, University of Houston.

  • Feng Chen

    • TCSUH and Department of Physics, University of Houston.

  • Bing Lv

    • The University of Texas at Dallas
    • TCSUH and Department of Chemistry, University of Houston.

  • Zhongjia Tang

    • TcSUH and Department of Chemistry, University of Houston
    • TCSUH and Department of Chemistry, University of Houston.

  • Arnold M Guloy

    • TCSUH and Department of Chemistry, University of Houston
    • TCSUH and Department of Chemistry, University of Houston.

  • Yu-Yi Xue

    • TCSUH and Department of Physics, University of Houston.

  • Paul C. W. Chu

    • TcSUH and Department of Physics, University of Houston; Lawrence Berkeley National Laboratory
    • University of Houston
    • TCSUH and Department of Physics, University of Houston; Lawrence Berkeley National Laboratory; Hong Kong University of Science and Technology.
    • TCSUH and Department of Physics, University of Houston; Lawrence Berkeley National Laboratory; Hong Kong University of Science and Technology