Spin resonance in AFe2Se2 with s-wave pairing symmetry

Abstract

We study spin resonance in the superconducting state of recently discovered alkali-intercalated iron selenide materials A_xFe_(2-y)Se_2 (A=K,Rb,Cs) in which the Fermi surface has only electron pockets. Recent angle-resolved photoemission spectroscopy (ARPES) studies [M. Xu et al., Phys. Rev. B 85, 220504(R) (2012)] were interpreted as strong evidence for s-wave gap in these materials, while the observation of the resonance peak in neutron scattering measurements [G. Friemel et al., Phys. Rev. B 85, 140511 (2012)] suggests that the gap must have different signs at Fermi surface points connected by the momentum at which the resonance has been observed. We consider recently proposed unconventional s+- superconducting state of A_xFe_(2-y)Se_2 with superconducting gap changing sign between the hybridized electron pockets. We argue that such a state supports a spin resonance. We compute the dynamical structure factor and show that it is consistent with the results of inelastic neutron scattering.

17 pages, 15 figures

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Cited by in corpus (10)

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• On the Remarkable Superconductivity of FeSe and its Close Cousins
• Spin fluctuations in iron pnictides and chalcogenides: From antiferromagnetism to superconductivity
• Optical conductivity of iron-based superconductors
• Structure of spin excitations in heavily electron-doped Li0.8Fe0.2ODFeSe superconductors
• Andreev spectroscopy of iron-based superconductors: temperature dependence of the order parameters and scaling of the ${\Delta }_{L,S}$ with $T_C$
• Collective modes in multiband superconductors: Raman scattering in iron selenides
• Heterostructural one-unit-cell FeSe/SrTiO3: from high-temperature superconductivity to topological states
• Spin resonance in the superconducting state of Li${}_{1-x}$Fe${}_x$ODFe${}_{1-y}$Se observed by neutron spectroscopy
• Transition from sign-reversed to sign-preserved Cooper-pairing symmetry in sulfur-doped iron selenide superconductors