Experimental elucidation of the origin of the `double spin resonances' in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$

Abstract

We report a combined study of the spin resonances and superconducting gaps for underdoped ($T_c=19$ K), optimally doped ($T_c=25$ K), and overdoped ($T_c=19$ K) Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ single crystals with inelastic neutron scattering and angle resolved photoemission spectroscopy. We find a quasi two dimensional spin resonance whose energy scales with the superconducting gap in all three compounds. In addition, anisotropic low energy spin excitation enhancements in the superconducting state have been deduced and characterized for the under and optimally doped compounds. Our data suggest that the quasi two dimensional spin resonance is a spin exciton that corresponds to the spin singlet-triplet excitations of the itinerant electrons. However, the intensity enhancements of the anisotropic spin excitations are dominated by the out-of-plane spin excitations of the ordered moments due to the suppression of damping in the superconducting state. Hence we offer a new interpretation of the double energy scales differing from previous interpretations based on anisotropic superconducting energy gaps, and systematically explain the doping-dependent trend across the phase diagram.

arXiv comment8 pages, 7 figures, 1 table. Accepted for publication on Physical Review B

References in corpus (39)

• Unconventional sign-reversing superconductivity in LaFeAsO_(1-x)F_x
• Antiferromagnetic order and spin dynamics in iron-based superconductors
• Resonant Spin Excitation in the High Temperature Superconductor Ba0.6K0.4Fe2As2
• Effects of Co substitution on thermodynamic and transport properties and anisotropic $H_{c2}$ in Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ single crystals
• Normal-State Spin Dynamics and Temperature-Dependent Spin Resonance Energy in an Optimally Doped Iron Arsenide Superconductor
• Fermi surface nesting induced strong pairing in iron-based superconductors
• Phenomenology of Photoemission Lineshapes of High Tc Superconductors
• The effect of collective spin-1 excitations on electronic spectra in high-Tc superconductors
• Two-dimensional resonant magnetic excitation in BaFe1.84Co0.16As2
• Nematic spin fluid in the tetragonal phase of BaFe2As2
• Neutron scattering as a probe of the Fe-pnicitide superconducting gap
• Three-dimensional Resonance in superconducting BaFe${}_{1.9}$Ni${}_{0.1}$As${}_2$
• Universal relation between magnetic resonance and superconducting gap in unconventional superconductors
• Static and Dynamic Magnetism in Underdoped Superconductor BaFe${}_{1.92}$Co${}_{0.08}$As${}_2$
• Symmetry of spin excitation spectra in the tetragonal paramagnetic and superconducting phases of 122-ferropnictides
• Neutron Scattering Resonance and the Fe-pnictide Superconducting Gap
• Crossover from weak to strong pairing in unconventional superconductors
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Dispersive Spin Fluctuations in the near optimally-doped superconductor Ba(Fe1-xCox)2As2 ($x$=0.065)
• Electron-doping evolution of the low-energy spin excitations in the iron arsenide BaFe${}_{2-x}$Ni${}_x$As${}_2$ superconductors
• Absolute cross-section normalization of magnetic neutron scattering data
• Spin gap and magnetic resonance in superconducting BaFe${}_{1.9}$NiAs${}_2$
• Splitting of resonance excitations in nearly optimally doped Ba(Fe0.94Co0.06)2As2: an inelastic neutron scattering study with polarization analysis
• Doping Dependence of Bilayer Resonant Spin Excitations in $(\mathbf{Y},\mathbf{Ca})\mathbf{B}{\mathbf{a}}_2\mathbf{C}{\mathbf{u}}_3{\mathbf{O}}_{6+\mathbf{x}}$
• Anisotropic and quasipropagating spin excitations in superconducting Ba(Fe0.926Co0.074)2As2
• Local magnetic anisotropy in BaFe${}_2$As${}_2$: a polarized inelastic neutron scattering study
• Electron doping evolution of the anisotropic spin excitations in BaFe2-xNixAs2
• Short-range cluster spin glass near optimal superconductivity in BaFe${}_{2-x}$Ni${}_x$As${}_2$
• Doping Dependence of Spin Dynamics in Electron-Doped Ba(Fe1-xCox)2As2
• Dispersion of the superconducting spin resonance in underdoped and antiferromagnetic Ba(Fe1-xCox)2As2
• Two energy scales in the magnetic resonance spectrum of electron and hole doped pnictide superconductors
• Anisotropic neutron spin resonance in underdoped superconducting NaFe1-xCoxAs
• Universality of dispersive spin-resonance mode in superconducting BaFe2As2
• Polarized neutron scattering studies of magnetic excitations in electron-overdoped superconducting BaFe${}_{1.85}$Ni${}_{0.15}$As${}_2$
• Magnonlike dispersion of spin resonance in Ni-doped BaFe${}_2$As${}_2$
• Magnetic resonance from the interplay of frustration and superconductivity
• Double magnetic resonance and spin anisotropy in Fe-based superconductors due to static and fluctuating antiferromagnetic orders
• Spin Excitations in BaFe1.84Co0.16As2 Superconductor Observed by Inelastic Neutron Scattering
• Neutron spin resonance as a probe of superconducting gap anisotropy in partially detwinned electron underdoped NaFe${}_{0.985}$Co${}_{0.015}$As

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• Fluctuations and pairing in Fe-based superconductors: Light scattering experiments
• Strong Spin Resonance Mode associated with suppression of soft magnetic ordering in Hole-doped Ba1-xNaxFe2As2
• Unusual suppression of a spin resonance mode with magnetic field in underdoped NaFe${}_{1-x}$Co${}_x$As: Evidence for orbital-selective pairing
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• Temperature and polarization dependence of low-energy magnetic fluctuations in nearly-optimal-doped NaFe${}_{0.9785}$Co${}_{0.0215}$As