Parametric localized modes in quadratic nonlinear photonic structures

We analyze two-color spatially localized modes formed by parametrically coupled fundamental and second-harmonic fields excited at quadratic (or chi-2) nonlinear interfaces embedded into a linear layered structure --- a quasi-one-dimensional quadratic nonlinear photonic crystal. For a periodic lattice of nonlinear interfaces, we derive an effective discrete model for the amplitudes of the fundamental and second-harmonic waves at the interfaces (the so-called discrete chi-2 equations), and find, numerically and analytically, the spatially localized solutions --- discrete gap solitons. For a single nonlinear interface in a linear superlattice, we study the properties of two-color localized modes, and describe both similarities and differences with quadratic solitons in homogeneous media.Comment: 9 pages, 8 figure

Magnetic-field-dependent zero-bias diffusive anomaly in Pb oxide-n-InAs structures: Coexistence of two- and three-dimensional states

The results of experimental and theoretical studies of zero-bias anomaly (ZBA) in the Pb-oxide-n-InAs tunnel structures in magnetic field up to 6T are presented. A specific feature of the structures is a coexistence of the 2D and 3D states at the Fermi energy near the semiconductor surface. The dependence of the measured ZBA amplitude on the strength and orientation of the applied magnetic field is in agreement with the proposed theoretical model. According to this model, electrons tunnel into 2D states, and move diffusively in the 2D layer, whereas the main contribution to the screening comes from 3D electrons.Comment: 8 double-column pages, REVTeX, 9 eps figures embedded with epsf, published versio

Realization of vertically aligned, ultra-high aspect ratio InAsSb nanowires on graphite

The monolithic integration of InAs1–xSbx semiconductor nanowires on graphitic substrates holds enormous promise for cost-effective, high-performance, and flexible devices in optoelectronics and high-speed electronics. However, the growth of InAs1–xSbx nanowires with high aspect ratio essential for device applications is extremely challenging due to Sb-induced suppression of axial growth and enhancement in radial growth. We report the realization of high quality, vertically aligned, nontapered and ultrahigh aspect ratio InAs1–xSbx nanowires with Sb composition (xSb(%)) up to ∼12% grown by indium-droplet assisted molecular beam epitaxy on graphite substrate. Low temperature photoluminescence measurements show that the InAs1–xSbx nanowires exhibit bright band-to-band related emission with a distinct redshift as a function of Sb composition providing further confirmation of successful Sb incorporation in as-grown nanowires. This study reveals that the graphite substrate is a more favorable platform for InAs1–xSbx nanowires that could lead to hybrid heterostructures possessing potential device applications in optoelectronics

Study of the High-Coercivity Material Based on ε-Fe2O3 Nanoparticles in the Silica Gel Matrix

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.We report the results of investigations of ε-Fe2O3 magnetic nanoparticles obtained by incipient wetness impregnation of silica gel. It was established that the obtained samples with an iron content of 12‒16% mass % containing ε-Fe2O3 nanoparticles with an average size of 10 nm on the silica gel surface exhibit a room-temperature coercivity of about 10 kOe. Along with fabrication simplicity, this fact makes the prepared samples promising for application as a magnetically hard material

Two-Dimensional Antiferromagnetic Correlations in an La_1.4Sr_1.6(Mn_0.9Co_0.1)₂O₇ Single Crystal

The temperature and field dependences of the magnetization, the electrical resistivity, and the magnetostriction of bilayer lanthanum manganite La1.4Sr1.6Mn2O7 single crystals and cobalt-doped La1.4Sr1.6(Mn0.9Cu0.1)(2)O-7 are measured. The magnetostriction of the cobalt-doped compound increases as compared to the initial La1.4Sr1.6Mn2O7 compound, and the magnetization and the magnetoresistance of the former compound change substantially. Powder and single-crystal neutron diffraction patterns are used to detect ferromagnetic ordering in La1.4Sr1.6(Mn0.9Co0.1)(2)O-7 at a temperature below T (C) similar to 45(2) K, and this ordering coexists with antiferromagnetic correlations, which develop at temperatures below T (C) similar to 80(5) K

Study of the High-Coercivity Material Based on ε-Fe2O3 Nanoparticles in the Silica Gel Matrix

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.We report the results of investigations of ε-Fe2O3 magnetic nanoparticles obtained by incipient wetness impregnation of silica gel. It was established that the obtained samples with an iron content of 12‒16% mass % containing ε-Fe2O3 nanoparticles with an average size of 10 nm on the silica gel surface exhibit a room-temperature coercivity of about 10 kOe. Along with fabrication simplicity, this fact makes the prepared samples promising for application as a magnetically hard material

[BETS]2\mathsf{_{2}}⋅C60\cdot{ C_{60 }} complex and BETS salts with square-planar platinate (II), nickelate (II) anions: (BETS)4{_{4}}⋅{\cdot} Pt(CN)4{_{4}}, (BETS)4{_{4}}⋅{\cdot} Ni(CN)4{_{4}}

The (BETS)$_{2}\cdot$C$_{60 }$ complex (1) and new radical cation salts based on bis(ethylenedithio)tetraselenafulvalene (BETS) with the square-planar [ Ni(CN)$_{4}$] $^{2-}$ , [ Pt(CN)$_{4}$] $^{2-}$ anions were synthesized: (BETS)$_{4}\cdot$Ni(CN)$_{4 }$(2), (BETS)$_{4}\cdot$Pt(CN)$_{4 }$(3). The crystal structure of 1 - 3 is layered. The layers consisting of C$_{60}$ molecules are alternated with the layers composed of BETS molecules in 1. The obtained complex is classified as molecular adduct in which the van der Waals interactions are predominant. The radical cation layers in the salt 2 are alternated with the anion layers along the ñ-direction of the unit cell. The salts retain metallic state down to 4.2 K. The band structure calculation of 2 shows 2-dimensional cylindrical Fermi surface, which is consistent with the $\theta$- type structure and its conductivity. Key words. Radical cation salts, bis(ethylenedithio)tetraselenafulvalene, tetracyanonickelate (II) anion, tetracyanoplatinate (II) anion, fullerene, crystal structure, electronic band structure calculation.