title: Quantum critical point in SmO(1-x)F(x)FeAs and oxygen vacancy induced by high fluorine dopant.
abstract: The local lattice and electronic structure of the high-T(c) superconductor SmO(1-x)F(x)FeAs as a function of F-doping have been investigated by Sm L(3)-edge X-ray absorption near-edge structure and multiple-scattering calculations. Experiments performed at the L(3)-edge show that the white line (WL) is very sensitive to F-doping. In the under-doped region (x ≤ 0.12) the WL intensity increases with doping and then it suddenly starts decreasing at x = 0.15. Meanwhile, the trend of the WL linewidth versus F-doping levels is just contrary to that of the intensity. The phenomenon is almost coincident with the quantum critical point occurring in SmO(1-x)F(x)FeAs at x ≃ 0.14. In the under-doped region the increase of the intensity is related to the localization of Sm-5d states, while theoretical calculations show that both the decreasing intensity and the consequent broadening of linewidth at high F-doping are associated with the content and distribution of oxygen vacancies.
authors.affiliation: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, People's Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Cheng
authors.forename: Shengqi
authors.initials: S
authors.lastname: Chu
authors.forename: Wangsheng
authors.initials: W
authors.lastname: Chu
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.forename: Jing
authors.initials: J
authors.lastname: Zhou
authors.forename: Linjuan
authors.initials: L
authors.lastname: Zhang
authors.forename: Haifeng
authors.initials: H
authors.lastname: Zhao
authors.forename: Ronghua
authors.initials: R
authors.lastname: Liu
authors.forename: Xianhui
authors.initials: X
authors.lastname: Chen
authors.forename: Augusto
authors.initials: A
authors.lastname: Marcelli
authors.forename: Ziyu
authors.initials: Z
authors.lastname: Wu