Evidence of quantum criticality in the phase diagram of K$_x$Sr$_{1-x}$Fe$_2$As$_2$ from measurements of transport and thermoelectricity

TL;DR

This study investigates the transport and thermoelectric properties of K_xSr_{1-x}Fe_2As_2, revealing quantum critical behavior near a critical doping level through resistivity and thermoelectric measurements.

Contribution

It provides experimental evidence of quantum criticality in K_xSr_{1-x}Fe_2As_2 by analyzing transport and thermoelectric properties across different doping levels.

Findings

Resistivity shows a crossover from Fermi liquid to linear T dependence at x_c=0.4.

Thermoelectric power exhibits a logarithmic T-dependence near the critical doping.

Results suggest coupling of electrons to spin fluctuations causes quantum critical behavior.

Abstract

The electrical transport and thermoelectric properties of K_xSr_{1-x}Fe_2As_2 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~T dependence at x_c=0.4. With further increasing x, rho(T) becomes non-linear again. The thermoelectric power S(T) exhibits a similar crossover with increasing x with a logarithmic T-dependence, S/T~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.