Analysis of hybrid modes in an optical waveguide bounded at one side by a gyromagnetic medium

Planar optical glass waveguides bounded at one side by a gyromagnetic substrate are investigated theoretically. Exact solutions are obtained for the phase and the attenuation constants of the hybrid mode. Field patterns of the hybrid wavefunction for the HE hybrid mode are also shown. A concrete example is given for the case when the substrate is of permalloy material. The analysis will be very useful for constructing integrated optical devices. A computer program was devised to obtain these results.     

Nonquasiparticle states in Co2MnSi evidenced through magnetic tunnel junction spectroscopy measurements

We investigate the effects of electronic correlations in the full-Heusler Co2MnSi, by combining a theoretical analysis of the spin-resolved density of states with tunneling-conductance spectroscopy measurements using Co2MnSi as electrode. Both experimental and theoretical results confirm the existence of so-called nonquasiparticle states and their crucial contribution to the finite-temperature spin polarization in this material.     

Multigap superconductivity in sesquicarbides La2C3 and Y2C3

A complex structure of the superconducting order parameter in Ln2C3 (Ln=La,Y) is demonstrated by muon spin relaxation measurements in their mixed state. The muon depolarization rate sigma v(T)] exhibits a characteristic temperature dependence that can be perfectly described by a phenomenological double-gap model for nodeless superconductivity. While the magnitude of two gaps is similar between La2C3 and Y2C3, a significant difference in the interband coupling between those two cases is clearly observed in the behavior of sigma v(T).     

Mechanism and control of periodic surface nanostructure formation with femtosecond laser pulses

Fundamental mechanism of femtosecond-laser-induced periodic surface nanostructure formation has been investigated under the condition using superimposed multiple shots at lower fluence than the single-pulse ablation threshold. With increasing the shot number of low-fluence fs-laser pulses, the periodic nanostructure develops through the bonding structure change of target material, the nanoscale ablation with optical near-fields induced around the high curvatures, and the excitation of surface plasmon polaritons (SPPs) to create the nano-periodicity in the surface structure. It is confirmed that non-thermal interaction at the surface plays the crucial role in the nanostructure formation. Based on the mechanism, we have demonstrated that the periodic nanostructure formation process can be controlled to fabricate a homogeneous nanograting on the target surface, using a two-step ablation process in air. The experimental results obtained represent exactly the nature of a single spatial standing SPP wave mode that generates periodically enhanced near-fields for the nanograting formation. The calculated results for a model target reproduce well the nanograting period and explain the characteristic properties observed in the experiment.     

Nanometric summation architecture based on optical near-field interaction between quantum dots

A nanoscale data summation architecture is proposed and experimentally demonstrated based on the optical near-field interaction between quantum dots. Based on local electromagnetic interactions between a few nanometric elements via optical near fields, we can combine multiple excitations at a certain quantum dot, which allows construction of a summation architecture. Summation plays a key role for content-addressable memory, which is one of the most important functions in optical networks.     

System-parameter dependence of the metallic phase of the non-doped 2D Hubbard model

Naito et al. reported that some non-doped T′-214-type compounds drive high-T_c superconductivity. The compounds are considered to be metallic since on-site Coulomb energy U is moderate and the Fermi surface is much deformed in these compounds. In order to confirm this picture and extract electronic structure information, we have examined the phase diagram of the metallic state of the 2D Hubbard model as a function of U and t′ (with t″ we fixed at − t′/2 here; t′ and t″ are the second- and third-neighbor transfer energies, respectively) by means of the variational Monte–Carlo method. We employed a Jastrow-type Gutzwiller trial wave function. In the studied range of U = 2–12, the boundary value for |t′| at which SDW disappears increases almost linearly with U. Jump-wise transition to the Mott insulator state was not observed. Using the boundary curve and experimental band parameter values, we estimate U  5 for T′-214 compounds. Preceding works are discussed in the last part.     

Unlocking the Hydrolytic Mechanism of GH92 α-1,2-Mannosidases: Computation Inspires the use of C-Glycosides as Michaelis Complex Mimics

The conformational changes in a sugar moiety along the hydrolytic pathway are key to understand the mechanism of glycoside hydrolases (GHs) and to design new inhibitors. The two predominant itineraries for mannosidases go via ^OS₂→B_2,5→¹S₅ and ³S₁→³H₄→¹C₄. For the CAZy family 92, the conformational itinerary was unknown. Published complexes of Bacteroides thetaiotaomicron GH92 catalyst with a S-glycoside and mannoimidazole indicate a ⁴C₁→⁴H₅/¹S₅→¹S₅ mechanism. However, as observed with the GH125 family, S-glycosides may not act always as good mimics of GH's natural substrate. Here we present a cooperative study between computations and experiments where our results predict the E₅→B_2,5/¹S₅→¹S₅ pathway for GH92 enzymes. Furthermore, we demonstrate the Michaelis complex mimicry of a new kind of C-disaccharides, whose biochemical applicability was still a chimera.     

Proton Conduction at High Temperature in High-Symmetry Hydrogen-Bonded Molecular Crystals of RuIII Complexes with Six Imidazole-Imidazolate Ligands

A new H-bonded crystal [Ru^III(Him)₃(Im)₃] with three imidazole (Him) and three imidazolate (Im⁻) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H-bonds between the Ru^III complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10⁻⁵ S cm⁻¹ at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [Ru^III(Him)₃(Im)₃] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state ²H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered.     

Selective Formation of Spinel Iron Oxide in Thin Films by Complexing Agent-Assisted Sol-Gel Processing

The structure of iron oxide was controlled by regulating the hydrolytic polymerization of aquo iron complexes with organic polydentate ligands such as diols. Iron oxides were prepared by calcining the precursor polymers obtained from iron nitrate nonahydrate and diols. When the diols were 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol, α-Fe₂O₃ with corundum structure appeared exclusively or as the main crystalline phase, in spite of the amount of diol used and the calcination temperature. In the case of 1,2-decanediol and 1,2-dodecanediol, when five moles of the diols were used to one mole of iron nitrate and the calcination temperatures were below 400°C, ψ-Fe₂O₃ with spinel structure appeared as the main phase and, when less than five moles of the diols were used, α-Fe₂O₃ appeared exclusively or as the main phase, irrespective of the calcination temperature. This tendency was also observed in thin films. Thus, a transparent magnetic film composed of γ-Fe₂O₃ could be prepared by applying a benzene solution of the iron polymer, obtained with 5 equivalents of 1,2-decanediol, on quartz and calcining the gel film at 350°C.