Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA.
Sci Rep. 2011;1:115. doi: 10.1038/srep00115. Epub 2011 Oct 19.
We report inelastic neutron scattering experiments on single crystals of superconducting Ba(0.67)K(0.33)Fe(2)As(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(0.67)Ka(0.33)Fe(2)As(2) are more complicated than those suggested from angle resolved photoemission experiments.
我们报告了在超导 Ba(0.67)K(0.33)Fe(2)As(2)（T(c)=38 K）单晶上的非弹性中子散射实验。除了确认在粉末样品中发现的共振之外，我们还发现正常态中的自旋激发在动量空间中沿着 Q(AFM)方向形成纵向拉长的椭圆，这与密度泛函理论预测一致。在冷却到 T(c)以下时，尽管共振保持了预期的动量各向异性，但低于共振能量的自旋激发在面内动量空间中变得几乎各向同性，并显著增加了它们的关联长度。这些结果表明，Ba(0.67)K(0.33)Fe(2)As(2)中的超导能隙结构比从角分辨光发射实验中所提出的结构更为复杂。
