Signatures of quantum criticality in hole-doped and chemically pressurized EuFe_2As_2 single crystals

Abstract

We study the effect of hole-doping and chemical pressure (isovalent doping) in single crystals of K${}_x$Eu${}_{1-x}$Fe${}_2$As${}_2$ and EuFe${}_2$(As${}_{1-y}$P${}_y$)${}_2$, respectively, by measurements of the thermopower, $S(T)$, and electrical resistivity, $\rho (T)$. The evolution of $S(T)$ upon doping indicates drastic changes of the electronic configuration at critical values $x_{\mathrm{cr}}=0.3$ and $y_{\mathrm{cr}}=0.21$, respectively, as the spin-density-wave transition is completely suppressed and superconductivity (SC) emerges. For the case of chemical pressure, the comparison with published ARPES measurements indicates a Lifshitz transition at $y_{cr}$. The temperature dependences $S(T)/T\propto \log T$ and $\Delta \rho \propto T$ observed in the normal state above the SC transition suggest quantum criticality in both systems.

arXiv commentPRB accepted

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• Thermoelectric properties of iron-based superconductors and parent compounds
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• Signatures of quantum criticality in the thermopower of Ba(Fe(1-x)Co(x))2As2
• Local and collective magnetism of EuFe${}_2$As${}_2$
• Observing the suppression of superconductivity in RbEuFe${}_4$As${}_4$ by correlated magnetic fluctuations
• Experimental evidence for the importance of Hund's exchange interaction for the incoherence of the charge carriers in iron-based superconductors
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• Pressure-temperature phase diagrams of CaK(Fe${}_{1-x}$Ni${}_x$)${}_4$As${}_4$ superconductors
• Electronic Nematicity Revealed by Torque Magnetometry in Iron Arsenide EuFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Linkage between scattering rates and superconductivity in doped ferropnictides
• Superconductivity in titanium-based pnictide oxide compounds
• Thermoelectric signature of quantum critical phase in a doped spin liquid candidate
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• Electronic Scattering Effects in Europium-Based Iron Pnictides
• Electronic structure and quantum criticality in Ba(Fe${}_{1-x-y}$Co${}_x$Mn${}_y$)${}_2$As${}_2$, an ARPES study
• Spin-correlation Driven Ferroelectric Quantum Criticality in a Perovskite Quantum Spin-liquid System, Ba3CuSb2O9