Electronic phase diagram of the iron-based high-Tc superconductor Ba(Fe1−xCox)2As2 under hydrostatic pressure (0≤x≤0.099)

We report comprehensive resistivity measurements of single-crystalline samples of the Ba(Fe1−xCox)2As2 high-Tc superconductor under hydrostatic pressure up to 2.75 GPa and over a broad concentration range, 0≤x≤0.099. We show that application of pressure progressively suppresses the spin-density wave (SDW) transition temperature, TSDW, in the underdoped regime (x≲0.051). There is no sign of pressure-induced superconductivity in the undoped BaFe2As2 down to 1.8 K but applied pressure dramatically enhances Tc in the underdoped regime 0.02≲x≲0.051. The effect of pressure on Tc is very small in the optimally and overdoped regimes 0.082≲x≲0.099. As a consequence, the dome of the superconducting phase extends to x≲0.02 under pressure. We discuss the implications of our findings in the context of a possible quantum phase transition between the SDW and superconducting phases.