Constant-energy plots of the magnetic excitations projected onto the H–K plane for the x=0.27 sample (panels a-c) as measured on Merlin. Panels d-f are fits to the data.
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The recent discovery of superconductivity with Tc up to 55 K in Fe-based materials has generated much excitement, yet the mechanism underpinning superconductivity in these ‘unconventional’ superconductors remains elusive.
Of the mechanisms proposed, spin-fluctuation-mediated superconductivity is among the most promising. As such, studies of magnetic excitations by means of inelastic neutron scattering are crucial. The simple crystal structure and availability of large crystals makes Fe1+yTe1-xSex particularly interesting. We have performed detailed inelastic neutron scattering studies of the magnetic excitations in Fe1+yTe1-xSex crystals with x=0.27 (non-superconducting) and x=0.49 (superconducting). These measurements reveal incommensurate 2d magnetic excitations up to energies of at least 300 meV. The spectrum exhibits four-fold symmetry about the (π,π) wave vector showing that a square lattice constitutes the fundamental unit cell for the magnetic interactions, as also found in the cuprates. The presence of incommensurate excitations and their evolution with energy are also similar to previous observations in the cuprates, which may suggest a common origin of superconductivity in both classes of materials.
MD Lumsden, AD Christianson, SE Nagler, HA Mook, C de la Cruz, MB Stone, DL Abernathy, GJ MacDougall, AS Sefat, MA McGuire, BC Sales, D Mandrus (Oak Ridge National Laboratory, USA), EA Goremychkin (ISIS, Argonne National Laboratory), T Guidi (ISIS)
Research date: March 2009
Contact: Dr MD Lumsden, firstname.lastname@example.org
Further information: MD Lumsden et al., Nat Phys 6 (2010) 182
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