Pressure dependence of the superconducting transition temperature of HgBa2CaCu2O6+delta as a function of carrier concentration

A phenomenological analysis for the pressure-induced change of the hole concentration in the CuO2 layers (n(H)) is developed. This effect along with thr pressure-induced change of the maximum value of critical temperature (T-c) enables us to take account of the external pressure dependence of T-c on different oxygen doping and different ambient T-c on the basis of the inverted parabolic relationship between T-c and n(H). Detailed calculations for HgBa2CaCu2O6+delta(delta=0.08 similar to 0.35) show that the T-c(P) curve with a saturation at large pressure in the nearly optimally doped but slightly underdoped material is located above the curve with a saturation at relatively low pressure in the slightly overdoped one, and that an experimental curve for the optimal doping lies between the two curves. It is found that the pressure coefficient (dT(c)/dP) decreases with increasing pressure and the initial pressure coefficient declines monotonously with the increase of hole concentration.