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

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

ABSTRACT

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.

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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 .
Physical Review B 05/2010; 81(18). DOI:10.1103/PhysRevB.81.184518 · 3.74 Impact Factor
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