2,469 research outputs found

    S wave superconductivity in newly discovered superconductor BaTi2_2Sb2_2O revealed by 121/123^{121/123}Sb-NMR/Nuclear Quadrupole Resonance measurements

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    We report the 121/123^{121/123}Sb-NMR/nuclear quadrupole resonance (NQR) measurements on the newly-discovered superconductor BaTi2_2Sb2_2O with a two-dimensional Ti2_2O square-net layer formed with Ti3+^{3+} (3d1d^1). NQR measurements revealed that the in-plane four-fold symmetry is broken at the Sb site below TAT_{\rm A} \sim 40 K, without an internal field appearing at the Sb site. These exclude a spin-density wave (SDW)/ charge density wave (CDW) ordering with incommensurate correlations, but can be understood with the commensurate CDW ordering at TAT_{\rm A}. The spin-lattice relaxation rate 1/T11/T_1, measured at the four-fold symmetry breaking site, decreases below superconducting (SC) transition temperature TcT_{\rm c}, indicative of the microscopic coexistence of superconductivity and the CDW/SDW phase below TAT_{\rm A}. Furthermore, 1/T11/T_1 of 121^{121}Sb-NQR shows a coherence peak just below TcT_{\rm c} and decreases exponentially at low temperatures. These results are in sharp contrast with those in cuprate and iron-based superconductors, and strongly suggest that its SC symmetry is classified to an ordinary s-wave state.Comment: 5 pages, 6 figure

    L^p boundedness of the wave operator for the one dimensional Schroedinger operator

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    Given a one dimensional perturbed Schroedinger operator H=-(d/dx)^2+V(x) we consider the associated wave operators W_+, W_- defined as the strong L^2 limits as s-> \pm\infty of the operators e^{isH} e^{-isH_0} We prove that the wave operators are bounded operators on L^p for all 1<p<\infty, provided (1+|x|)^2 V(x) is integrable, or else (1+|x|)V(x) is integrable and 0 is not a resonance. For p=\infty we obtain an estimate in terms of the Hilbert transform. Some applications to dispersive estimates for equations with variable rough coefficients are given.Comment: 26 page

    Organometalic carbosilane polymers containing vanadium and their preparation

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    The present invention concerns a new organometallic polymer material containing in part a vanadium-siloxane linkage (V-0-Si), which has excellent resistance to heat and oxidation and a high residue ratio after high temperature treatment in a non-oxidizing atmosphere, for example, nitrogen, argon, helium, ammonia, or hydrogen

    Method for producing heat-resistant semi-inorganic compounds

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    The method for producing a heat resistant, semi-inorganic compound is discussed. Five examples in which various alcohols, phenols, and aromatic carbonic acids are used to test heat resistance and solubility are provided

    Inverse Scattering at a Fixed Quasi-Energy for Potentials Periodic in Time

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    We prove that the scattering matrix at a fixed quasi--energy determines uniquely a time--periodic potential that decays exponentially at infinity. We consider potentials that for each fixed time belong to L3/2L^{3/2} in space. The exponent 3/2 is critical for the singularities of the potential in space. For this singular class of potentials the result is new even in the time--independent case, where it was only known for bounded exponentially decreasing potentials.Comment: In this revised version I give a more detailed motivation of the class of potentials that I consider and I have corrected some typo

    Dynamical formation of correlations in a Bose-Einstein condensate

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    We consider the evolution of NN bosons interacting with a repulsive short range pair potential in three dimensions. The potential is scaled according to the Gross-Pitaevskii scaling, i.e. it is given by N2V(N(xixj))N^2V(N(x_i-x_j)). We monitor the behavior of the solution to the NN-particle Schr\"odinger equation in a spatial window where two particles are close to each other. We prove that within this window a short scale interparticle structure emerges dynamically. The local correlation between the particles is given by the two-body zero energy scattering mode. This is the characteristic structure that was expected to form within a very short initial time layer and to persist for all later times, on the basis of the validity of the Gross-Pitaevskii equation for the evolution of the Bose-Einstein condensate. The zero energy scattering mode emerges after an initial time layer where all higher energy modes disperse out of the spatial window. We can prove the persistence of this structure up to sufficiently small times before three-particle correlations could develop.Comment: 36 pages, latex fil
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