Institut des Nanosciences de Paris, CNRS UMR 7588, Université Pierre et Marie Curie Paris 6, Paris, France.
J Phys Condens Matter. 2010 Nov 24;22(46):465701. doi: 10.1088/0953-8984/22/46/465701. Epub 2010 Nov 4.
We present the synthesis and the tunneling spectroscopy study of superconducting FeSe(0.5)Te(0.5) (T(c) = 14 K), SmFeAsO(0.85) (T(c) = 54 K) and SmFeAsO(0.9)F(0.1) (T(c) = 45 K). The samples were characterized by Rietveld refinement of x-ray diffraction patterns and transport as well as temperature-dependent magnetic measurements. Tunneling experiments on FeSe(0.5)Te(0.5) revealed a single superconducting gap ∼ 1 meV in BCS-like tunneling conductance spectra. In SmFeAsO(0.85) and SmFeAsO(0.9)F(0.1), however, more complex spectra were observed, characterized by two gap-like structures at ∼ 4 and ∼ 10 meV. These spectra are qualitatively understood assuming a two-band superconductor with a 's ±' order parameter. We show that, depending on the sign relation between the pairing amplitudes in the two bands, the interband quasiparticle scattering has a crucial effect on the shape of the tunneling spectra. On the other hand, single-gap spectra found in FeSe(0.5)Te(0.5) are more compatible with a disorder-induced 's '-wave gap, due to the Se-Te substitution.
我们展示了超导 FeSe(0.5)Te(0.5)(T(c)=14 K)、SmFeAsO(0.85)(T(c)=54 K)和 SmFeAsO(0.9)F(0.1)(T(c)=45 K)的合成和隧道谱研究。通过 X 射线衍射图谱的 Rietveld 精修以及输运和温度相关的磁测量对样品进行了表征。FeSe(0.5)Te(0.5)的隧道实验揭示了在 BCS 型隧道电导谱中存在约 1 meV 的单个超导能隙。然而，在 SmFeAsO(0.85)和 SmFeAsO(0.9)F(0.1)中，观察到更为复杂的谱，其特征在于约 4 和约 10 meV 的两个能隙结构。通过假设具有's ±' 序参量的双能带超导体，可以定性地理解这些谱。我们表明，取决于两个能带中配对振幅的符号关系，带间准粒子散射对隧道谱的形状有至关重要的影响。另一方面，由于 Se-Te 取代，在 FeSe(0.5)Te(0.5)中发现的单隙谱更符合由无序诱导的's -波间隙。
