4,305 research outputs found

    Lattice-form dependent orbital shape and charge disproportionation in charge- and orbital-ordered manganites

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    The orbital shapes and charge disproportionations at nominal Mn3+^{3+} and Mn4+^{4+} sites for the charge- and orbital-ordered phases have been studied on half-doped manganites Pr(Sr0.1_{0.1}Ca0.9_{0.9})2_2Mn2_2O7_7 and Eu0.5_{0.5}Ca1.5_{1.5}MnO4_4 with double-layer and single-layer Mn-O networks, respectively, by means of x-ray structural analyses, in comparison with Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 with the pseudo cubic network. In a single-layer Eu0.5_{0.5}Ca1.5_{1.5}MnO4_4 system, the (y2z2y^2-z^2)/(z2x2z^2-x^2)-type orbital shape is observed, while the (3y2r23y^2-r^2)/(3x2r23x^2-r^2)-type orbital shape in a pseudo cubic Pr0.5_{0.5}Ca0.5_{0.5}MnO3_3 system. In a double-layer Pr(Sr0.1_{0.1}Ca0.9_{0.9})2_2Mn2_2O7_7 system, the orbital shape is found to undergo a large change upon thermally induced rotation of orbital stripe. Furthermore, clear charge disproportionation is observed for the pseudo cubic and double-layer systems, while not in the single-layer system. These results indicate that the orbital shape and charge disproportionation are sensitive to the dimension of Mn-O network.Comment: 12 page, 5 figures, 11 table

    Zeeman Spectroscopy of the Star Algebra

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    We solve the problem of finding all eigenvalues and eigenvectors of the Neumann matrix of the matter sector of open bosonic string field theory, including the zero modes, and switching on a background B-field. We give the discrete eigenvalues as roots of transcendental equations, and we give analytical expressions for all the eigenvectors.Comment: (1, 25) pages, 2 Figure

    Enhanced quasiparticle heat conduction of the multigap superconductor Lu2Fe3Si5

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    The thermal transport measurements have been made on the Fe-based superconductor Lu2Fe3Si5 (Tc ~ 6 K) down to a very low temperature Tc/120. The field and temperature dependences of the thermal conductivity confirm the multigap superconductivity with fully opened gaps on the whole Fermi surfaces. In comparison to MgB2 as a typical example of the multigap superconductor in a p-electron system, Lu2Fe3Si5 reveals a remarkably enhanced quasiparticle heat conduction in the mixed state. The results can be interpreted as a consequence of the electronic correlations derived from Fe 3d-electrons.Comment: 5 pages, 4 figure

    Electrically Enhanced Free Dendrite Growth in Polar and Non-polar Systems

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    We describe the electrically enhanced growth of needle crystals from the vapor phase, for which there exists a morphological instability above a threshold applied potential. Our improved theoretical treatment of this phenomenon shows that the instability is present in both polar and non-polar systems, and we provide an extension of solvability theory to include electrical effects. We present extensive experimental data for ice needle growth above the electrical threshold, where at T=5T=-5C high-velocity shape-preserving growth is observed. These data indicate that the needle tip assumes an effective radius} RR^{\ast} which is nearly independent of both supersaturation and the applied potential. The small scale of RR^{\ast} and its response to chemical additives suggest that the needle growth rate is being limited primarily by structural instabilities, possibly related to surface melting. We also demonstrate experimentally that non-polar systems exhibit this same electrically induced morphological instability
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