Xu H C, Niu X H, Xu D F, Jiang J, Yao Q, Chen Q Y, Song Q, Abdel-Hafiez M, Chareev D A, Vasiliev A N, Wang Q S, Wo H L, Zhao J, Peng R, Feng D L
State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China.
Phys Rev Lett. 2016 Oct 7;117(15):157003. doi: 10.1103/PhysRevLett.117.157003.
FeSe exhibits a novel ground state in which superconductivity coexists with a nematic order in the absence of any long-range magnetic order. Here, we report on an angle-resolved photoemission study on the superconducting gap structure in the nematic state of FeSe_{0.93}S_{0.07}, without the complications caused by Fermi surface reconstruction induced by magnetic order. We find that the superconducting gap shows a pronounced twofold anisotropy around the elliptical hole pocket near Z (0, 0, π), with gap minima at the end points of its major axis, while no detectable gap is observed around Γ (0, 0, 0) and the zone corner (π, π, k_{z}). The large anisotropy and nodal gap distribution demonstrate the substantial effects of the nematicity on the superconductivity and thus put strong constraints on current theories.
FeSe呈现出一种新颖的基态，其中超导性在不存在任何长程磁序的情况下与向列序共存。在此，我们报道了一项关于FeSe₀.₉₃S₀.₀₀₇向列态超导能隙结构的角分辨光电子能谱研究，该研究不受磁序诱导的费米面重构所带来的复杂性影响。我们发现，超导能隙在靠近Z（0, 0, π）的椭圆空穴口袋周围呈现出明显的二重各向异性，在其长轴端点处能隙最小，而在Γ（0, 0, 0）和区角（π, π, kₓ）周围未观察到可检测到的能隙。这种大的各向异性和节点能隙分布证明了向列性对超导性的实质性影响，从而对当前理论施加了严格限制。
