Origin of critical-temperature enhancement of an iron-based high-T_c superconductor, LaFeAsO_{1-x}F_{x} : NMR study under high pressure

Abstract

Nuclear magnetic resonance (NMR) measurements of an iron (Fe)-based superconductor LaFeAsO_{1-x}F_x (x = 0.08 and 0.14) were performed at ambient pressure and under pressure. The relaxation rate 1/T_1 for the overdoped samples (x = 0.14) shows T-linear behavior just above T_c, and pressure application enhances 1/T_1T similar to the behavior of T_c. This implies that 1/T_1T = constant originates from the Korringa relation, and an increase in the density of states at the Fermi energy D(E_F) leads to the enhancement of T_c. In the underdoped samples (x = 0.08), 1/T_1T measured at ambient pressure also shows T-independent behavior in a wide temperature range above T_c. However, it shows Curie-Weiss-like T dependence at 3.0 GPa accompanied by a small increase in T_c, suggesting that predominant antiferromagnetic fluctuation suppresses development of superconductivity or remarkable enhancement of T_c. The qualitatively different features between underdoped and overdoped samples are systematically explained by a band calculation with hole and electron pockets.

References in corpus (18)

• Superconductivity at 38 K in the iron arsenide (Ba1-xKx)Fe2As2
• Magnetic Order versus superconductivity in the Iron-based layered La(O1-xFx)FeAs systems
• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Superconductivity up to 37 K in (A1-xSrx)Fe2As2 with A=K and Cs
• The electronic phase diagram of the LaO1-xFxFeAs superconductor
• Coexistence of the spin-density-wave and superconductivity in the (Ba,K)Fe2As2
• Evolution from Itinerant Antiferromagnet to Unconventional Superconductor with Fluorine Doping in La(O_{1-x}F_{x})FeAs Revealed by ^{75}As and ^{139}La Nuclear Magnetic Resonance
• Commensurate Spin Density Wave in LaOFeAs: A Local Probe Study
• ${}^{75}$As NMR studies of superconducting LaO${}_{0.9}$F${}_{0.1}$FeAs
• Superconductivity under high pressure in LaFeAsO
• NMR relaxation rate in superconducting pnictides: extended $s_{\pm }$ scenario
• Superfluid density of the $\pm$s-wave state for the iron-based superconductors
• Pseudogap and Superconductivity in Iron-Based Layered Superconductor studied by Fluctuation-Exchange Approximation
• Doping evoluton of antiferromagnetic order and structural distortion in LaFeAsO${}_{1-x}$F${}_x$
• Two superconducting gaps in LaFeAsO0.92F0.08 revealed by 75As nuclear quadrupole resonance
• Pressure-induced superconductivity in Iron pnictide compound SrFe2As2
• Correlated pressure effects on structure and superconductivity in LaFeAsO0.9F0.1
• 75As-NMR studies on La FeAsO1-xFx (x=0.14) under a pressure of 3GPa

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• Non-Fermi-Liquid-Like Behaviors and Superconductivity Driven by Orbital Fluctuations in Iron Pnictides: Analysis by Fluctuation-Exchange Approximation
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• Experimental evidence of $T_c$ enhancement without the influence of spin fluctuations: NMR study on LaFeAsO_{1-x}H_x under a pressure of 3.0 GPa
• Diamond Magnetometry of Meissner Currents in a Superconducting Film
• Homogeneous coexistence of SDW and SC states in CaFe(1-x)Co(x)AsF studied by nuclear magnetic resonance
• Quantum Phase transition under pressure in a heavily hydrogen-doped iron-based superconductor LaFeAsO
• Understanding the re-entrant superconducting phase diagram of an iron-pnictide Ca${}_4$Al${}_2$O${}_6$Fe${}_2$(As${}_{1-x}$P${}_x$)${}_2$