Enhanced superconductivity and moderate spin fluctuations suppressed at low energies in heavily electron-doped La1111-based superconductor

Abstract

To elucidate the origin of re-enhanced high-$T_c$ phase in the heavily electron-doped Fe-pnictides, systematic ${}^{75}$As NMR studies are performed on heavily electron-doped LaFe$Pn$O${}_{0.75}$H${}_{0.25}$ by controlling the pnictogen height ($h_{Pn}$) from the Fe plane through the substitution at $Pn$(=As) site with Sb or P. The measurements of nuclear spin relaxation rate (1/$T_1$) and Knight shift ($K$) reveal that the moderate spin fluctuations at high temperatures are suppressed toward low temperatures. Such characteristic spin fluctuations with gap like feature at low energies are more enlarged in higher $T_c$ compounds with higher $h_{Pn}$, while those are totally suppressed in non-superconducting compounds with lower $h_{Pn}$. This implies that the contribution of the finite energy part in the spin fluctuation spectrum is crucial for enhancing $T_c$ in the heavily electron-doped regime. This is in contrast to many cases of typical Fe-based compounds with hole and electron Fermi surfaces of similar sizes, where the spin fluctuations at low energies develop significantly at low temperatures. The features in the heavily electron-doped states are discussed in relation with the characteristics of the faint hole Fermi surface derived from $d_{xy}$ orbital that rises when $h_{Pn}$ is high, together with the enhanced electron correlation effects.

6 pages, 4 figures, Accepted for publication in Phys. Rev. B

References in corpus (22)

• The electronic phase diagram of the LaO1-xFxFeAs superconductor
• Fe-based high temperature superconductivity with Tc=31K bordering an insulating antiferromagnet in (Tl,K)FexSe2 Crystals
• Iron-Based Superconductors: current status of materials and pairing mechanism
• Structure determination and coexistence of superconductivity and antiferromagnetic order in (Li0.8Fe0.2)OHFeSe
• Superconductivity at 32 K in single crystal Rb${}_{0.78}$Fe${}_2$Se${}_{1.78}$}
• Superconductivity at 32K and anisotropy in Tl0.58Rb0.42Fe1.72Se2 crystals
• Transport properties of the new Fe-based superconductor KxFe2Se2 (Tc = 33 K)
• Bipartite magnetic parent phases in the iron-oxypnictide superconductor
• NMR Study in the Iron-Selenide Rb0.74Fe1.6Se2: Determination of the Superconducting Phase as Iron Vacancy-Free Rb0.3Fe2Se2
• Superconductivity in LaFeAs${}_{1-x}$P${}_x$O: effect of chemical pressures and bond covalency
• Superconductivity at Tc = 44 K in LixFe2Se2(NH3)y
• Synthesis and post-annealing effects of alkaline-metal-ethylenediamine-intercalated superconductors Ax(C2H8N2)yFe2-zSe2 (A = Li, Na) with Tc = 45 K
• 77Se NMR Investigation of the K(x)Fe(2-y)Se(2) High Tc Superconductor (Tc=33K)
• Pressure versus concentration tuning of the superconductivity in Ba(Fe(1-x)Cox)2As2
• Emergence of Novel Antiferromagnetic Order Intervening between Two Superconducting Phases in LaFe(As_1-x_P_x_)O: 31P-NMR Studies
• Evolution of the Phase Diagram of LaFeP${}_{1-x}$As${}_x$O${}_{1-y}$F${}_y$ ($y$ = 0 -- 0.1)
• Wide applicability of high $T_c$ pairing originating from coexisting wide and incipient narrow bands in quasi one dimension
• Possible Superconducting Symmetry and Magnetic Correlations in K0.8Fe2Se2: A 77Se-NMR Study
• Quantum critical behavior in heavily doped LaFeAsO${}_{1-x}$H${}_x$ pnictide superconductors analyzed using nuclear magnetic resonance
• Superconductivity and normal state properties of single-crystalline Tl0.47Rb0.34Fe1.63Se2 as seen via 77Se and 87Rb NMR
• Three superconducting phases with different categories of pairing in hole- and electron-doped LaFeAs${}_{1-x}$P${}_x$O
• Importance of dxy orbital and electron correlation in iron-based superconductors revealed by phase diagram for 1111-system

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