Evolution of spin excitations into the superconducting state in FeTe1-xSex

Nature Physics (Impact Factor: 20.6). 07/2009; DOI: 10.1038/nphys1512
Source: OAI

ABSTRACT The origin of the superconducting state in the recently discovered Fe-based materials is the subject of intense scrutiny. Neutron scattering and NMR measurements have already demonstrated a strong correlation between magnetism and superconductivity. A central unanswered question concerns the nature of the normal-state spin fluctuations that may be responsible for the pairing. Here we present inelastic neutron scattering measurements from large single crystals of superconducting and non-superconducting Fe1+yTe1-xSex. These measurements indicate a spin fluctuation spectrum dominated by two-dimensional incommensurate excitations extending to energies greater than 250;meV. Most importantly, the spin excitations in Fe1+yTe1-xSex have four-fold symmetry about the (1, 0) wavevector (square-lattice (pi,pi) point). Moreover, the excitations are described by the identical wavevector and can be characterized by the same model as the normal-state spin excitations in the high-TC cuprates. These results demonstrate commonality between the magnetism in these classes of materials, which perhaps extends to a common origin for superconductivity.

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