Neutron spin resonance as a probe of Fermi surface nesting and superconducting gap symmetry in Ba0.67K0.33(Fe1−xCox)2As2
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We use inelastic neutron scattering to study the energy and wave-vector dependence of the superconductivity-induced resonance in hole-doped Ba0.67K0.33(Fe1−xCox)2As2 (x=0 and 0.08 with Tc≈37 and 28 K, respectively). In previous work on electron-doped Ba(Fe0.963Ni0.037)2As2 (TN=26K and Tc=17 K), the resonance is found to peak sharply at the antiferromagnetic (AF) ordering wave vector QAF along the longitudinal direction, but disperses upwards away from QAF along the transverse direction [Kim et al., Phys. Rev. Lett. 110, 177002 (2013)]. For hole-doped x=0 and 0.08 without AF order, we find that the resonance displays a ringlike upward dispersion away from QAFalong both the longitudinal and transverse directions. By comparing these results with calculations using the random phase approximation, we conclude that the dispersive resonance is a direct signature of isotropic superconducting gaps arising from nested hole-electron Fermi surfaces.
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Zhang, Rui, Wang, Weiyi, Maier, Thomas A., et al.. "Neutron spin resonance as a probe of Fermi surface nesting and superconducting gap symmetry in Ba0.67K0.33(Fe1−xCox)2As2." Physical Review B, 98, no. 6 (2018) American Physical Society: https://doi.org/10.1103/PhysRevB.98.060502.