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), 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 Letter
