title: Highly Anisotropic and Twofold Symmetric Superconducting Gap in Nematically Ordered FeSe_{0.93}S_{0.07}.
abstract: 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.
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: H C
authors: HC
authors: Xu
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: X H
authors: XH
authors: Niu
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: D F
authors: DF
authors: Xu
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: J
authors: J
authors: Jiang
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: Q
authors: Q
authors: Yao
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: Q Y
authors: QY
authors: Chen
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: Q
authors: Q
authors: Song
authors: Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China.|Faculty of science, Physics Department, Fayoum University, 63514 Fayoum, Egypt.
authors: M
authors: M
authors: Abdel-Hafiez
authors: Institute of Experimental Mineralogy, Russian Academy of Sciences, 142432 Chernogolovka, Moscow District, Russia.|Institute of Physics and Technology, Ural Federal University, 620002 Ekaterinburg, Russia.
authors: D A
authors: DA
authors: Chareev
authors: Institute of Physics and Technology, Ural Federal University, 620002 Ekaterinburg, Russia.|Low Temperature Physics and Superconductivity Department, M.V. Lomonosov Moscow State University, 119991 Moscow, Russia.
authors: A N
authors: AN
authors: Vasiliev
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: Q S
authors: QS
authors: Wang
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: H L
authors: HL
authors: Wo
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: J
authors: J
authors: Zhao
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: R
authors: R
authors: Peng
authors: State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China.
authors: D L
authors: DL
authors: Feng