Abstract
We report inelastic neutron scattering experiments on single crystals of superconducting Ba 0.67K 0.33Fe 2As 2 (T c = 38 K). In addition to confirming the resonance previously found in powder samples, we find that spin excitations in the normal state form longitudinally elongated ellipses along the Q AFM direction in momentum space, consistent with density functional theory predictions. On cooling below T c, while the resonance preserves its momentum anisotropy as expected, spin excitations at energies below the resonance become essentially isotropic in the in-plane momentum space and dramatically increase their correlation length. These results suggest that the superconducting gap structures in Ba 0.67Ka 0.33Fe 2As 2 are more complicated than those suggested from angle resolved photoemission experiments.
Original language | English |
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Article number | 115 |
Journal | Scientific Reports |
Volume | 1 |
DOIs | |
State | Published - 2011 |
Funding
This work is supported in part by the US Department of Energy, Division of Materials Science, Basic Energy Sciences, through DOE DE-FG02-05ER46202 and by the US Department of Energy, Division of Scientific User Facilities, Basic Energy Sciences. SPINS and MACS utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-0454672 and No. DMR-0944772, respectively. The work at the Institute of Physics, Chinese Academy of Sciences, is supported by the Chinese Academy of Sciences. T.A.M. would like to acknowledge support from the Center for Nanophase Materials Sciences, which is sponsored at ORNL by Basic Energy Sciences, U.S. DOE.