Phase Diagram and Quantum Critical Point in Newly Discovered Superconductors: SmO_{1-x}F_xFeAs

Abstract

The magnetic fluctuations associated with a quantum critical point (QCP) are widely believed to cause the non-Fermi liquid behaviors and unconventional superconductivities, for example, in heavy fermion systems and high temperature cuprate superconductors. Recently, superconductivity has been discovered in iron-based layered compound $La{O}_{1-x}{F}_{x}FeAs$ with $T_c$=26 K\cite{yoichi}, and it competes with spin-density-wave (SDW) order\cite{dong}. Neutron diffraction shows a long-rang SDW-type antiferromagnetic (AF) order at $\sim 134$ K in LaOFeAs\cite{cruz,mcguire}. Therefore, a possible QCP and its role in this system are of great interests. Here we report the detailed phase diagram and anomalous transport properties of the new high-Tc superconductors $Sm{O}_{1-x}{F}_{x}FeAs$ discovered by us\cite{chenxh}. It is found that superconductivity emerges at $x\sim$0.07, and optimal doping takes place in the $x\sim$0.20 sample with highest $T_c\sim$54 K. While $T_c$ increases monotonically with doping, the SDW order is rapidly suppressed, suggesting a QCP around $x\sim$0.14. As manifestations, a linear temperature dependence of the resistivity shows up at high temperatures in the $x<0.14$ regime, but at low temperatures just above $T_c$ in the $x>0.14$ regime; a drop in carrier density evidenced by a pronounced rise in Hall coefficient are observed, which mimic the high-$T_c$ cuprates. The simultaneous occurrence of order, carrier density change and criticality makes a compelling case for a quantum critical point in this system.

10 pages, 4 figures

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• Competing Orders and Spin-Density-Wave Instability in La(O${}_{1-x}$F${}_x$)FeAs
• Anomalous Transport Phenomena in Fermi Liquids with Strong Magnetic Fluctuations
• Non-Fermi liquid behavior in the magnetotransport of CeMIn5 (M: Co and Rh): Striking similarity between quasi 2D heavy fermion and high-Tc cuprates
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Cited by in corpus (8)

• Coherence-incoherence crossover in the normal state of iron-oxypnictides and importance of the Hund's rule coupling
• The BCS-like gap in superconductor SmFeAsO_0.85F_0.15
• Structure and Magnetic Order in the NdFeAs(O,F) Superconductor System
• Comparative High Field Magneto-Transport of Rare Earth Oxypnictides with Maximum Transition Temperatures
• Upper critical fields well above 100 T for the superconductor SmFeAsO${}_{0.85}$F${}_{0.15}$ with T${}_c$ = 46 K
• Heteroepitaxial growth and optoelectronic properties of layered iron oxyarsenide, LaFeAsO
• Structural and critical current properties in polycrystalline SmO1-xFxFeAs
• Cu, Pu and Fe high Tc superconductors: all the same mechanism!