Precise measurement of the CP violation parameter sin2φ1 in B0→(cc¯)K0 decays

We present a precise measurement of the CP violation parameter sin2φ1 and the direct CP violation parameter A(f) using the final data sample of 772×10(6) BB[over ˉ] pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. One neutral B meson is reconstructed in a J/ψK(S)(0), ψ(2S)K(S)(0), χ(c1)K(S)(0), or J/ψK(L)(0) CP eigenstate and its flavor is identified from the decay products of the accompanying B meson. From the distribution of proper-time intervals between the two B decays, we obtain the following CP violation parameters: sin2φ1=0.667±0.023(stat)±0.012(syst) and A(f)=0.006±0.016(stat)±0.012(syst).     

Electric field control of nonvolatile four-state magnetization at room temperature

We find the realization of large converse magnetoelectric (ME) effects at room temperature in a magnetoelectric hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62μ(B)/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients.     

The study of below and above band-edge imperfection states in In2S3 solar energy materials

β-In₂S₃ is a nontoxic buffer layer material usually used in a thin-film solar cell due to a lot of vacancies and surface states naturally existing in the crystal to assist in photoelectric conversion. Transition metal (TM)-incorporated β-In₂S₃ has also been proposed to increase conversion efficiency in In₂S₃ since multi-photons absorption by intermediate band (IB) would happen in the sulfide. In this paper, single crystals of undoped and Nb-doped β-In₂S₃ have been grown by the chemical vapor transport (CVT) method using ICl₃ as a transport agent. Optical properties of the imperfection states of the crystals are probed by thermoreflectance (TR), photoconductivity (PC), photoluminescence (PL), surface photoconductive response (SPR), optical absorption and photo–voltage–current (photo V–I) measurements. The TR and optical-absorption measurements confirmed that the undoped and Nb-doped β-In₂S₃ are direct semiconductors with energy gap of 1.935 eV for undoped β-In₂S₃, 1.923 eV for β-In₂S₃:Nb_0.005, and 1.901 eV for β-In₂S₃:Nb_0.01. For undoped β-In₂S₃, PC and PL measurements are used to characterize defect transitions below band gap. The above band-edge transitions of undoped β-In₂S₃ have also been evaluated using PL, PC, and SPR measurements. For the evaluation of Nb-doped β-In₂S₃, an intermediate band with energy of ∼0.4 eV below the conduction band edge has been detected in the TR measurements in both β-In₂S₃:Nb_0.005 and β-In₂S₃:Nb_0.01. The photo V–I measurements also verified that the photoelectric-conversion efficiency would be enhanced in the β-In₂S₃ with higher niobium content. Based on the experimental analyses, the optical behavior of the defects, surface states, and IB (formed by Nb) in the In₂S₃ crystals is thus explored.     

Self‐formed Schottky barrier induced selector‐less RRAM for cross‐point memory applications

We propose a selector‐less Pr_0.7Ca_0.3MnO₃ (PCMO) based resistive‐switching RAM (RRAM) for high‐density cross‐point memory array applications. First, we investigate the inhomogeneous barrier with an effective barrier height (Φ_eff), i.e., self‐formed Schottky barrier. In addition, a scalable 4F² selector‐less cross‐point 1 kb RRAM array has been successfully fabricated, demonstrating set, reset, and read operation for high cell efficiency and high‐density memory applications. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multi-stacked organic light-emitting diodes using zinc oxide nanoparticle interfacial layers

Stacked organic light-emitting diodes (SOLEDs) with 30-nm nanoparticle (NP) interfacial layers were investigated. Zinc oxide (ZnO) was used as an interfacial layer between two green polymer (GP) layers. SOLEDs with NP interfacial layers had higher device efficiency than did a single-unit device due to the high probability of exciton recombination that originated from the Auger electron-assisted energy up-conversion process. Although the current density and luminance of SOLEDs with ZnO NP interfacial layers were smaller than those of the reference device, the efficiency was doubled because of the big band alignment difference and the large band gap between GP and ZnO NP interfacial layers, which induced more radiative-exciton recombination.     

All-optical time-division demultiplexing and spatial pulse routing with a GaAs/AlGaAs microring resonator

We report what is to our knowledge the first demonstration of all-optical time-division demultiplexing and spatial pulse routing in a compact nonlinear GaAs/AlGaAs microring resonator operating at 1.55 microm . Switching is through the refractive-index change induced by two-photon absorption. The switching time of the device, limited by the ring-charging time and the recombination time of the induced carriers, is measured to be 30 ps. The switching on-off contrast, limited by the slight mismatch between the input and output coupling coefficients, exceeds 8 dB. The device can be used for time-division multiplexing as well.     

Control of device performances of phosphorescent white organic light-emitting diodes by managing charge transport properties of host materials

Interlayer-free phosphorescent white organic light-emitting diodes (PHWOLEDs) with a mixed-host emitting structure in red emitting layer were developed and device performances were investigated according to the host composition in the red emitting layer. Device performances could be effectively managed by a simple change of host materials in the red emitting layer. A high quantum efficiency was obtained in PHWOLEDs with electron transport-type host in the red emitting layer and red emission was strong in PHWOLEDs with mixed-host in the red emitting layer. In addition, stable color performances were obtained in electron transport-type host rich devices.     

Shape-dependent local internal stress of α-Cr2O3 nanocrystal fabricated by pulsed laser ablation

The α-Cr₂O₃ single-crystal nanocondensates were fabricated by pulsed laser ablation in air and characterized by analytical electron microscopy regarding shape-dependent local internal stress of the anisotropic crystal. The nanocondensates formed predominantly as rhombohedra with well-developed surfaces and occasionally hexagonal plate with thin edges and blunt corners. Such nanocondensates showed Raman shift for the CrO₆ polyhedra, indicating a local compressive stress up to ca. 4 GPa on the average. Careful analysis of the lattice fringes revealed a local compressive stress (0.5% strain) at the thin edge of the hexagonal plates and a local tensile stress (0.3–1.0% strain) near the relaxed , , and (0 0 0 1) surfaces of truncated rhombohedra. The combined effects of nanosize, capillarity force at sharp edge, and specific surface relaxation account for the retention of a local internal compressive stress built up in an anisotropic crystal during a very rapid heating–cooling process.     

A sonochemical-assisted synthesis and annealing temperature effect of La<Subscript>0.7</Subscript>Sr<Subscript>0.3</Subscript>MnO<Subscript>3</Subscript> nanoparticles

This paper reports on the sonochemical-assisted synthesis of La_0.7Sr_0.3MnO₃ (LSMO) nanoparticles (NPs) which have a single-crystalline perovskite structure. The average particle size of LSMO NPs was controlled from about 40 to 120 nm by changing the annealing temperatures from 750 to 1050°C. The particle size, electrical resistivity, and ferromagnetic transition temperature of LSMO NPs were strongly dependent on the annealing temperature. A substantial decrease in resistivity and an enhancement in the insulator–metal transition temperature were found on increasing the annealing temperature. Furthermore, the enhancement in magnetization and paramagnetic–ferromagnetic (PM–FM) transition temperatures was observed as the annealing temperature increases.     

Doubly Excited <Superscript>1,3</Superscript><Emphasis Type="Italic">P</Emphasis><Superscript>e</Superscript> Resonance States of the Positronium Negative Ion with Coulomb and Screened Coulomb Potentials

We have investigated the doubly excited ^1,3 P ^e resonance states of positronium negative ion with Coulomb and screened Coulomb potentials using highly accurate correlated exponential wavefunctions. For Coulomb interaction, the stabilization and the complex-rotation methods are employed to extract resonance parameters (resonance positions and widths). We have obtained two ¹ P ^e resonances and three ³ P ^e resonances below the n = 3 Ps threshold. In addition to Feshbach resonances lying below n = 3 Ps threshold, we have calculated one ³ P ^e shape resonances lying above the Ps (n = 2) threshold. For screened Coulomb (Yukawa) interaction, we employ the stabilization method to extract resonance parameters as functions screening parameter. The resonance energies and widths for ^1,3 P ^e resonance states of Ps⁻ below the n = 3 Ps threshold for different screening parameters ranging from infinity (Coulomb case) to small values are reported, along with the Ps(3S) and Ps(3P) threshold energies. The screened Coulomb results for the ^1,3 P ^e resonance states are reported for the first time in the literature.