  Low temperature specific heat (SH) was measured on the FeAs-based
superconducting single crystals Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ and high
pressure synthesized polycrystalline samples SmFeAsO$_{0.9}$F$_{0.1}$. It is
found that the sharp SH anomaly $\Delta C/T|_{T_c}$ in
Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ reaches an unexpected high value of 98 mJ/mol
K$^2$, about one order of magnitude larger than that of
SmFeAsO$_{0.9}$F$_{0.1}$ ($6\sim8$ mJ/mol K$^2$) samples, suggesting very high
normal state quasiparticle density of states in FeAs-122 than in FeAs-1111.
Furthermore, we found that the electronic SH coefficient $\gamma_e(T)$ of
Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ is weakly temperature dependent and increases
almost linearly with the magnetic field in low temperature region, which may
indicate that the hole-doped FeAs-122 system contains a dominant component with
a full superconducting gap, although we cannot rule out the possibility of a
small component with anisotropic or nodal gap. A detailed analysis reveals that
the $\gamma_e(T)$ of Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ cannot be fitted with a
single gap of s-wave symmetry probably due to the multigap effect. These
results indicate clear difference between the properties of the superconducting
state of the holed-doped Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ and the F-doped
LnFeAsO (Ln = rare earth elements) systems, which we believe is originated from
the complex Fermi surface structures in different systems.
