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Doping dependence of the spin excitations in the Fe-based superconductors Fe 1 + y Te 1 − x Se<mml:math xmlns:mml="http://www.…

2013; American Physical Society; Volume: 87; Issue: 22 Linguagem: Inglês

10.1103/physrevb.87.224410

1550-235X

A. D. Christianson, M. D. Lumsden, Karol Marty, C. H. Wang, Stuart Calder, D. L. Abernathy, M. B. Stone, H. A. Mook, Michael A. McGuire, Athena S. Sefat, B. C. Sales, David Mandrus, E. A. Goremychkin,

Physics of Superconductivity and Magnetism

The Fe${}_{1+y}$Te${}_{1\ensuremath{-}x}$Se${}_{x}$ series of materials is one of the prototype families of Fe-based superconductors. To provide further insight into these materials, we present systematic inelastic neutron scattering measurements of the low-energy spin excitations for $x=0.27$, 0.36, 0.40, and 0.49. These measurements show an evolution of incommensurate spin excitations towards the (1/2,1/2,0) wave vector with doping. Concentrations ($x=0.40$ and 0.49) which exhibit the most robust superconducting properties have spin excitations closest to (1/2,1/2,0) and also exhibit a strong spin resonance in the spin excitation spectrum below ${T}_{c}$. The resonance signal appears to be closer to (1/2,1/2,0) than the underlying spin excitations. We discuss the possible relationship between superconductivity and spin excitations at the (1/2,1/2,0) wave vector and the role that interstitial Fe may play.