The unconventional superconductivity in the newly discovered iron-based superconductors is intimately related to its multi-band/multi-orbital nature. Here we report the comprehensive orbital characters of the low-energy three-dimensional electronic structure in BaFe1.85Co0.15As2 by studying the polarization and photon energy dependence of angle-resolved photoemission data. While the distributions of the dxz, dyz, and d 3z 2 −r 2 orbitals agree with the prediction of density functional theory, those of the dxy and d x 2 −y 2 orbitals show remarkable disagreement with theory. Our results point out the inadequacy of the existing band structure calculations, and more importantly, provide a foundation for constructing the correct microscopic model of iron pnictides.
The electrochemical behavior of UCl 4 and UCl 3 in LiCl-KCl eutectic melt was studied at 723-823 K by different electrochemical methods. Electroreduction of U͑IV͒ in LiCl-KCl melt occurs via two successive steps involving transfer of one and three electrons. The diffusion coefficients of U͑IV͒ and U͑III͒ were determined by linear sweep voltammetry, chronopotentiometry, and chronoamperometry. The values found by these methods are in a good agreement with each other. The standard rate constants for the redox reaction U͑IV͒ + e − → U͑III͒ were calculated from cyclic voltammetry data and for the discharge process U͑III͒ + 3e − → U by using the impedance spectroscopy method. The values of constants testify that the redox process proceeds quasireversibly, mostly under diffusion control, while electrodeposition is mainly controlled by the rate of charge transfer. The formal standard potentials of E U͑IV͒/U͑III͒ * , E U͑IV͒/U * , and E U͑III͒/U * were determined by different electrochemical methods and some thermodynamic properties of UCl 4 and UCl 3 dissolved in a LiCl-KCl eutectic melt were calculated. The influence of oxide ions on the electrochemical behavior of the LiCl-KCl-UCl 4 melt was studied.
The C 2v symmetry of the W(110) surface influences strongly the spin-polarized Dirac-cone-like surface state within a spin-orbit-induced symmetry gap. We present a detailed angle-resolved photoemission study with sand p-polarized light along three different symmetry lines. The Dirac-cone-like feature appears along H and S, while it is strongly deformed along N. A twofold 3 symmetry of the d-type surface state is identified from photoemission experiments using linearly polarized light. Our results are well described by model calculations based on an effective Hamiltonian with C 2v symmetry. The flattened Dirac cone of the surface state is caused by hybridization with bulk continuum states of 1 and 2 symmetry. The spin texture of this state obtained from the model calculations shows a quasi-one-dimensional behavior. This finding opens a new avenue in the study of d-electron-based persistent spin helix systems and/or weak topological insulators.
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