Critical scaling of transport properties in the phase diagram of iron pnictide superconductors K_(x)Sr_(1-x)Fe_(2)As_(2) and K_(x)Ba_(1-x)Fe_(2)As_(2)

摘要

We present a systematic study of resistivity and thermoelectric power for iron pnictide systems K_(x)Sr_(1-x)Fe_(2)As_(2) and K_(x)Ba_(1-x)Fe_(2)As_(2) for 0 < x < 1. Both systems show a similar phase diagram with an antiferromagnetic (AFM) phase on the low-doping side and a superconducting dome-shaped phase at higher doping. The AFM phase intersects the superconducting phase boundary. The extrapolation of the AFM phase boundary to zero temperature defines a critical doping of x_(c) approx 0.4. We show that the electrical and thermoelectric transport properties above the superconducting T_(c) obey a characteristic temperature scaling behavior at x_(c). The crossover and scaling property indicates the existence of a (possibly hidden) magnetic quantum critical point in the phase diagram of the 122 iron pnictides. The results of this investigation prove the significance of magnetic fluctuations in iron pnictide superconductors.