18,025 research outputs found
Resonant x-ray scattering study on multiferroic BiMnO3
Resonant x-ray scattering is performed near the Mn K-absorption edge for an
epitaxial thin film of BiMnO3. The azimuthal angle dependence of the resonant
(003) peak (in monoclinic indices) is measured with different photon
polarizations; for the channel a 3-fold symmetric oscillation
is observed in the intensity variation, while the scattering
intensity remains constant. These features are accounted for in terms of the
peculiar ordering of the manganese 3d orbitals in BiMnO3. It is demonstrated
that the resonant peak persists up to 770 K with an anomaly around 440 K; these
high and low temperatures coincide with the structural transition temperatures,
seen in bulk, with and without a symmetry change, respectively. A possible
relationship of the orbital order with the ferroelectricity of the system is
discussed.Comment: 14 pages, 4 figure
Generalized W-Class State and its Monogamy Relation
We generalize the W class of states from qubits to qudits and prove
that their entanglement is fully characterized by their partial entanglements
even for the case of the mixture that consists of a W-class state and a product
state .Comment: 12 pages, 1 figur
Depressed clad hollow optical fiber with fundamental LP01 mode cut-off
We propose a depressed clad hollow optical fiber with fundamental (LP01) mode cut-off suitable for high power short-wavelength, especially three-level, fiber laser operation by introducing highly wavelength dependent losses at longer wavelengths. The cut-off characteristic of such fiber structure was investigated. A Yb-doped depressed clad hollow optical fiber laser generating 59.1W of output power at 1046nm with 86% of slope efficiency with respect to the absorbed pump power was realised by placing the LP01 mode cut-off at ~1100nm
Cluster Model of Decagonal Tilings
A relaxed version of Gummelt's covering rules for the aperiodic decagon is
considered, which produces certain random-tiling-type structures. These
structures are precisely characterized, along with their relationships to
various other random tiling ensembles. The relaxed covering rule has a natural
realization in terms of a vertex cluster in the Penrose pentagon tiling. Using
Monte Carlo simulations, it is shown that the structures obtained by maximizing
the density of this cluster are the same as those produced by the corresponding
covering rules. The entropy density of the covering ensemble is determined
using the entropic sampling algorithm. If the model is extended by an
additional coupling between neighboring clusters, perfectly ordered structures
are obtained, like those produced by Gummelt's perfect covering rules.Comment: 10 pages, 20 figures, RevTeX; minor changes; to be published in Phys.
Rev.
Subthreshold characteristics of pentacene field-effect transistors influenced by grain boundaries.
Grain boundaries in polycrystalline pentacene films significantly affect the electrical characteristics of pentacene field-effect transistors (FETs). Upon reversal of the gate voltage sweep direction, pentacene FETs exhibited hysteretic behaviours in the subthreshold region, which was more pronounced for the FET having smaller pentacene grains. No shift in the flat-band voltage of the metal-insulator-semiconductor capacitor elucidates that the observed hysteresis was mainly caused by the influence of localized trap states existing at pentacene grain boundaries. From the results of continuous on/off switching operation of the pentacene FETs, hole depletion during the off period is found to be limited by pentacene grain boundaries. It is suggested that the polycrystalline nature of a pentacene film plays an important role on the dynamic characteristics of pentacene FETs
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