Gap structure in the electron-doped Iron-Arsenide Superconductor Ba(Fe0.92Co0.08)2As2: low-temperature specific heat study

New Journal of Physics (Impact Factor: 3.56). 01/2010; 12(2). DOI: 10.1088/1367-2630/12/2/023006
Source: arXiv


We report the field and temperature dependence of the low-temperature
specific heat down to 400 mK and in magnetic fields up to 9 T of the
electron-doped Ba(Fe0.92Co0.08)2As2 superconductor. Using the phonon specific
heat obtained from pure BaFe2As2 we find the normal state Sommerfeld
coefficient to be 18 mJ/mol.K^2 and a condensation energy of 1.27 J/mol. The
temperature dependence of the electronic specific heat clearly indicate the
presence of the low-energy excitations in the system. The magnetic field
variation of field-induced specific heat cannot be described by single clean s-
or d-wave models. Rather, the data require an anisotropic gap scenario which
may or may not have nodes. We discuss the implications of these results.

Download full-text


Available from: Krzysztof Gofryk
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report a doping, magnetic field, and low-temperature-dependent study of the specific heat of the iron-arsenide Ba(Fe1-xCox)2As2 at underdoped (x=0.045) , optimal-doped (x=0.08) and overdoped ( x=0.103 and 0.105) regimes. By subtracting the lattice specific heat the temperature and magnetic field dependence of the electronic specific heat has been studied. The temperature and field dependencies of the superconducting part of Cp exhibit similar behavior for all doping concentrations. The temperature variation in the electronic specific heat as well as its field dependence cannot be described by a single isotropic s -wave gap, pointing to a complex gap structure in the system. The lack of doping dependence indicates that the gap structure does not change significantly as a function of doping. We also observe a significant residual linear term of unknown origin in the specific heat of Ba(Fe1-xCox)2As2 which suggests that inhomogeneity may be an important factor in Co-doped BaFe2As2 .
    Full-text · Article · May 2010 · Physical Review B
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The response of the worldwide scientific community to the discovery in 2008 of superconductivity at Tc = 26 K in the Fe-based compound LaFeAsO_{1-x}F_x has been very enthusiastic. In short order, other Fe-based superconductors with the same or related crystal structures were discovered with Tc up to 56 K. Many experiments were carried out and theories formulated to try to understand the basic properties of these new materials and the mechanism for Tc. In this selective critical review of the experimental literature, we distill some of this extensive body of work, and discuss relationships between different types of experiments on these materials with reference to theoretical concepts and models. The experimental normal-state properties are emphasized, and within these the electronic and magnetic properties because of the likelihood of an electronic/magnetic mechanism for superconductivity in these materials. Comment: 148 two-column typeset pages, including 96 figures, 35 tables and 583 references; pdf: 8.0 MB; v2: significantly enhanced and expanded; accepted for publication in Advances in Physics
    Preview · Article · May 2010 · Advances In Physics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An extensive calorimetric study of the normal- and superconducting-state properties of Ba(Fe1-xCox)2As2 is presented for 0 < x < 0.2. The normal-state Sommerfeld coefficient increases (decreases) with Co doping for x < 0.06 (x > 0.06), which illustrates the strong competition between magnetism and superconductivity to monopolize the Fermi surface in the underdoped region and the filling of the hole bands for overdoped Ba(Fe1-xCox)2As2. All superconducting samples exhibit a residual electronic density of states of unknown origin in the zero-temperature limit, which is minimal at optimal doping but increases to the normal-state value in the strongly under- and over-doped regions. The remaining specific heat in the superconducting state is well described using a two-band model with isotropic s-wave superconducting gaps. Comment: Submitted to Europhysics Letters
    Full-text · Article · Jul 2010 · EPL (Europhysics Letters)
Show more