Superconductivity in pure and Co-doped BaFe$_2$As$_2$ under high pressure*

In-plane resistivity of pure and Co-doped BaFe$_2$As$_2$ single crystals was measured up to $\sim 75$ kbar in liquid media using piston-cylinder ($P < 25$ kbar) and modified Bridgman ($P < 75$ kbar) pressure cells. A dome-like rigeon of superconductivity with $T_c^{max}$ at $\sim 55$ kbar was induced in pure BaFe$_2$As$_2$. Dome-like $T_c(P)$ behavior was also observed for underdoped Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. For overdoped samples $T_c$ decrease under pressure, followed by filamentary superconductivity, was measured. The evolution of the pressure dependencies of the normal state resistivity, initial $dT_c/dP)$, maximum $T_c$ observed under pressure, with Co doping will be discussed.