Influences of decoherence on the generation of a macroscopic superposition state using weak cross-Kerr effect

Considering a system in which a single photon and a coherent field propagate through a Kerr medium, when the weak cross-Kerr interaction between the coherent state and the single photon under decoherence is involved, this paper derives analytically a macroscopic superposition state by the superoperator method and investigates the influences of decoherence on the coherence properties of the obtained state. It finds that the macroscopic superposition state will experience evolution from a pure superposition state to a mixed state in a dissipative environment and the Kerr effect makes the field display a periodic revival from decoherence for a short time.     

Characteristics of guided waves in indefinite-medium waveguides

We have presented a discussion on the guided waves in the indefinite-medium waveguides. The characteristic equations describing TE and TM guided waves have been derived. Aiming mainly at the TE guided waves, we have analyzed the existence conditions for the guided and surface modes for four distinct cases, respectively. A number of exotic properties have been revealed in such waveguides, such as the coexistence of forward and backward modes, the absence of fundamental modes, the existence of surface modes and the relaxed requirements for waveguide core constitutive parameters. Numerical results have confirmed our analyses.     

Raman spectroscopy of synthetic organic pigments used in 20th century works of art

Raman microscopy allows a non‐destructive characterisation of inorganic and organic painting materials such as pigments and organic dyestuffs. The objectives of this study are the more recent organic pigments typically present in paintings and other art works from the 20th century. More than 20 organic synthetic pigments from different chemical classes could be identified by Raman spectroscopy using different excitation wavelengths (457.9, 476.5, 487.9, 514.5, 632.8, and 1064 nm). To evaluate the performance for real paint samples, varying paint mixtures of the Hansa Yellow pigment PY 3 and the binding medium Mowilith, a polyvinyl acetate (PVAC) compound, were characterised; PY 3 was determined at a 1 wt% level in the binder. In addition, commercial tube paints containing the quinacridone violet PV 19 were studied. The pigment was clearly identified in all of these more complex oil and acrylic paints. Finally, alizarin (PR 83) and a green copper phthalocyanine pigment (PG 7) could unambiguously be identified by Raman microscopy in the painting ‘Woman with mandolin in yellow and red’ of Max Beckmann dating 1950. The discovery of a red naphthol AS pigment by Raman spectroscopy in a sample from the ‘Three field workers’ by Georg Baselitz (1964/1965) demonstrated that in some cases complementary chromatographic methods are needed for a comprehensive identification of the organic pigments. Copyright © 2008 John Wiley & Sons, Ltd.     

Magnetic properties,electronic structure,and optical properties of the filled skutterudite BaFe4Sb12

The magnetic properties, electronic structure, and optical properties of the filled skutterudite BaFe₄Sb₁₂ are calculated by the first-principles full-potential linearized augmented plane wave (FPLAPW) plus local orbital method. It is found that the local spin density approximation (LSDA) method appears more accurate than the generalized gradient approximation (GGA) method in calculating the electronic structures and optical properties of this compound. Furthermore, our calculated lattice constant and spin magnetic moments with the LSDA method are in overall better agreement with experiment. In contrast with recent experiment, our calculations are in good agreement with experimental reflectivity spectra and optical conductivity spectrum.     

Thermally stable luminescence of blue LiSrPO4:Eu2+ phosphor for near-UV light-emitting diodes

Blue phosphor, LiSrPO₄:Eu²⁺, was prepared by solid-state reaction method under a weak reductive atmosphere and investigated by means of photoluminescence, concentration quenching process, and temperature dependence of luminescence. These results show that LiSrPO₄:Eu²⁺ can be efficiently excited by the UV-visible light of 250–440 nm and exhibits bright blue emission. Furthermore, Eu²⁺-doped LiSrPO₄ phosphor shows high thermally stable luminescence comparable to commercial phosphor BaMgAl₁₀O₁₇:Eu²⁺ (BAM). Two bright blue LEDs were fabricated by incorporating an InGaN-based near-UV chip with the obtained phosphor LiSrPO₄:Eu²⁺ and BAM, respectively. Their luminescence properties were compared based on different forward-bias currents. All the characteristics suggest that LiSrPO₄:Eu²⁺ is a good blue phosphor candidate for creating white light in phosphor-conversion white LEDs.     

Formation of pancakelike Ising domains and giant magnetic coercivity in ferrimagnetic LuFe2O4

We have studied quasi-two-dimensional multiferroic LuFe2O4 with strong charge-spin-lattice coupling, in which low-temperature coercivity approaches an extraordinary value of 9 T in single crystals. The enhancement of the coercivity is connected to the collective freezing of nanoscale pancakelike ferrimagnetic domains with large uniaxial magnetic anisotropy ("Ising pancakes"). Our results suggest that collective freezing in low-dimensional magnets with large uniaxial anisotropy provides an effective mechanism to achieve enhanced coercivity. This observation may help identify novel approaches for synthesis of magnets with enhanced properties.     

Anomalous transport properties and phase diagram of the FeAs-based SmFeAsO1-xFx superconductors

We report the detailed phase diagram and anomalous transport properties of Fe-based high-T_{c} superconductors SmFeAsO1-xFx. It is found that superconductivity emerges at x approximately 0.07, and optimal doping takes place in the x approximately 0.20 sample with the highest T_{c} approximately 54 K. T_{c} increases monotonically with doping; the anomaly in resistivity from structural phase or spin-density-wave order is rapidly suppressed, suggesting a quantum critical point around x approximately 0.14. As manifestations, a linear temperature dependence of the resistivity shows up at high temperatures in the x<0.14 regime but at low temperatures just above T_{c} in the x>0.14 regime; a drop in carrier density evidenced by a pronounced rise in the Hall coefficient is observed below the temperature of the anomaly peak in resistivity. A scaling behavior is observed between the Hall angle and temperature: cottheta_{H} proportional, variantT;{1.5} for all samples with different x in SmFeAsO1-xFx system.