Evidence of quantum criticality in the phase diagram of KxSr1-xFe2As2 from measurements of transport and thermoelectricity

The electrical transport and thermoelectric properties of KxSr1-xFe2As2 are investigated for 0 <= x <= 1. The resistivity rho(T) shows a crossover from Fermi-liquid-like temperature dependence at small x to linear rho similar to T dependence at x(c)similar or equal to 0.4. With further increasing of x, rho(T) becomes nonlinear again. The thermoelectric power S(T) exhibits a similar crossover with increasing x with a logarithmic T dependence, S/T similar to ln(T), near the critical doping x(c). These results provide evidence for a quantum critical behavior due to the coupling of low-energy conduction electrons to two-dimensional spin fluctuations.