Doping dependence of the pressure response of Tc in the SmO1-xFxFeAs superconductors

The superconducting transition temperature of the high-T(c) SmO(1-x)F(x)FeAs superconductors increases monotonically as the F-doping level x increases to 0.20. High-pressure magnetization experiments reveal a strong sensitivity of T(c) to interatomic distances in the underdoped regime (x <= 0.12) with the pressure coefficient of T(c) d(ln T(c))/dP being strongly positive, However, as the doping level increases further to x = 0.15, we find that this sensitivity is strongly suppressed and at the same time, d(ln T(c))/dP sharply switches over to assume negative values with T(c) decreasing with increasing applied pressure. The aburpt change in the pressure response of the superconducting properties of the SmO(1-x)F(x)FeAs phases coincides with the putative existence of a quantum critical point (QCP) near x approximate to 0.14, as proposed by resistivity and Hall effect measurements.