Nodal gap structure in Fe-based superconductors due to the competition between orbital and spin fluctuations
Nodal gap structure in Fe-based superconductors due to the competition between orbital and spin fluctuations
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DOI：
10.1103/physrevb.88.045115
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发表时间：
2013-07-11
影响因子：
3.7
通讯作者：
Kontani, Hiroshi
中科院分区：
文献类型：
--
作者：
Saito, Tetsuro;Onari, Seiichiro;Kontani, Hiroshi
为了理解BaFe_2（As，P）（2）中节隙结构的起源，我们基于三维十轨道Hubbard模型，考虑四极相互作用，研究了三维节隙结构.在这个模型中，强烈的自旋和轨道波动时，使用随机相位近似。通过求解Eliashberg能隙方程，我们得到了类孔费米面和类电子费米面之间由于强自旋（轨道）涨落而发生（不发生）符号反转的完全能隙s波态，即所谓的s（+/-）波态.当自旋和轨道涨落都很强时，在正交相附近实现，我们在s（++）波和s（+/-）波态的交叉区域得到一个节s波态。由于k空间中的吸引力和排斥力的竞争，得到的节点s波态在类电子费米面上具有环形节点。相比之下，由于轨道涨落的作用，类孔费米面上的超导能隙是完全带隙的。本文解释了实验观察到的BaFe_2（As，P）（2）各向异性能隙结构的主要特征。
To understand the origin of the nodal gap structure realized in BaFe2(As, P)(2), we study the three-dimensional gap structure based on the three-dimensional ten-orbital Hubbard model with quadrupole interaction. In this model, strong spin and orbital fluctuations develop when the random-phase approximation is used. By solving the Eliashberg gap equation, we obtain the fully gapped s-wave state with (without) sign reversal between holelike and electronlike Fermi surfaces due to strong spin (orbital) fluctuations, the so-called s(+/-)-wave (s(++)-wave) state. When both spin and orbital fluctuations develop strongly, which will be realized near the orthorhombic phase, we obtain a nodal s-wave state in the crossover region between the s(++)-wave and s(+/-)-wave states. The nodal s-wave state obtained possesses loop-shaped nodes on electronlike Fermi surfaces, due to the competition between attractive and repulsive interactions in k space. In contrast, the superconducting gaps on the holelike Fermi surfaces are fully gapped due to orbital fluctuations. The present study explains the main characteristics of the anisotropic gap structure in BaFe2(As, P)(2) observed experimentally.