131 research outputs found
Effect of annealing on the specific heat of optimally doped Ba(FeCo)As
We report the temperature dependence of the low-temperature specific heat
down to 400 mK of the electron-doped Ba(FeCo)As
superconductors. We have measured two samples extracted from the same batch:
first sample has been measured just after preparation with no additional heat
treatment. The sample shows =20 K, residual specific heat
=3.6 mJ/mol K and a Schottky-like contribution at low
temperatures. A second sample has been annealed at 800 for two weeks
and shows = 25 K and =1.4 mJ/mol~K. By subtracting
the lattice specific heat, from pure BaFeAs, the temperature
dependence of the electronic specific heat has been obtained and studied. For
both samples the temperature dependence of clearly indicate the
presence of low-energy excitations in the system. Their specific heat data
cannot be described by single clean s- or d-wave models and the data requires
an anisotropic gap scenario which may or may not have nodesComment: SCES 2010, 5 pages, 2 figure
Calorimetric Evidence for Nodes in the Overdoped Ba(FeCo)As
We present low-temperature specific heat of the electron-doped
Ba(FeCo)As, which does not show any indication of
an upturn down to 400 mK, the lowest measuring temperature. The lack of a
Schottky-like feature at low temperatures or in magnetic fields up to 9 Tesla
enables us to identify enhanced low-temperature quasiparticle excitations and
to study anisotropy in the linear term of the specific heat. Our results can
not be explained by a single or multiple isotropic superconducting gap, but are
consistent with multi-gap superconductivity with nodes on at least one Fermi
surface sheet.Comment: 5 pages 4 figure
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