Soft striped magnetic fluctuations competing with superconductivity in Fe_{1+x}Te

Neutron spectroscopy is used to investigate the magnetic fluctuations in Fe_{1+x}Te - a parent compound of chalcogenide superconductors. Incommensurate "stripe-like" excitations soften with increased interstitial iron concentration. The energy crossover from incommensurate to stripy fluctuations defines an apparent hour-glass dispersion. Application of sum rules of neutron scattering find that the integrated intensity is inconsistent with an S=1 Fe^{2+} ground state and significantly less than S=2 predicted from weak crystal field arguments pointing towards the Fe^{2+} being in a superposition of orbital states. The results suggest that a highly anisotropic order competes with superconductivity in chalcogenide systems.
Comment: (7 pages and 8 pages supplementary information, to be published in Physical Review B)