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231.
Choi SK Coldea R Kolmogorov AN Lancaster T Mazin II Blundell SJ Radaelli PG Singh Y Gegenwart P Choi KR Cheong SW Baker PJ Stock C Taylor J 《Physical review letters》2012,108(12):127204
We report inelastic neutron scattering measurements on Na2IrO3, a candidate for the Kitaev spin model on the honeycomb lattice. We observe spin-wave excitations below 5 meV with a dispersion that can be accounted for by including substantial further-neighbor exchanges that stabilize zigzag magnetic order. The onset of long-range magnetic order below T(N)=15.3 K is confirmed via the observation of oscillations in zero-field muon-spin rotation experiments. Combining single-crystal diffraction and density functional calculations we propose a revised crystal structure model with significant departures from the ideal 90° Ir-O-Ir bonds required for dominant Kitaev exchange. 相似文献
232.
Adachi I Aihara H Asner DM Aulchenko V Aushev T Aziz T Bakich AM Bay A Bhardwaj V Bhuyan B Bischofberger M Bondar A Bozek A Bračko M Browder TE Chen P Cheon BG Chilikin K Chistov R Cho K Choi SK Choi Y Dalseno J Danilov M Doležal Z Drásal Z Eidelman S Epifanov D Fast JE Gaur V Gabyshev N Garmash A Goh YM Golob B Haba J Hara K Hara T Hayasaka K Hayashii H Higuchi T Horii Y Hoshi Y Hou WS Hsiung YB Hyun HJ Iijima T Ishikawa A Itoh R Iwabuchi M Iwasaki Y Iwashita T Julius T Kapusta P Katayama N 《Physical review letters》2012,108(17):171802
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). 相似文献
233.
Sangsu Park Seungjae Jung Manzar Siddik Minseok Jo Jubong Park Seonghyun Kim Wootae Lee Jungho Shin Daeseok Lee Godeuni Choi Jiyong Woo Euijun Cha Byoung Hun Lee Hyunsang Hwang 《固体物理学:研究快报》2012,6(11):454-456
We propose a selector‐less Pr0.7Ca0.3MnO3 (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 (Φeff), 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) 相似文献
234.
Seung Yoon Ryu Sung Hyun Kim Chang Su Kim Sungjin Jo Jun Yeob Lee 《Current Applied Physics》2012,12(5):1378-1380
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. 相似文献
235.
Xiu Yang Minseok Choi Guang Lin George Em Karniadakis 《Journal of computational physics》2012,231(4):1587-1614
Realistic representation of stochastic inputs associated with various sources of uncertainty in the simulation of fluid flows leads to high dimensional representations that are computationally prohibitive. We investigate the use of adaptive ANOVA decomposition as an effective dimension–reduction technique in modeling steady incompressible and compressible flows with nominal dimension of random space up to 100. We present three different adaptivity criteria and compare the adaptive ANOVA method against sparse grid, Monte Carlo and quasi-Monte Carlo methods to evaluate its relative efficiency and accuracy. For the incompressible flow problem, the effect of random temperature boundary conditions (modeled as high-dimensional stochastic processes) on the Nusselt number is investigated for different values of correlation length. For the compressible flow, the effects of random geometric perturbations (simulating random roughness) on the scattering of a strong shock wave is investigated both analytically and numerically. A probabilistic collocation method is combined with adaptive ANOVA to obtain both incompressible and compressible flow solutions. We demonstrate that for both cases even draconian truncations of the ANOVA expansion lead to accurate solutions with a speed-up factor of three orders of magnitude compared to Monte Carlo and at least one order of magnitude compared to sparse grids for comparable accuracy. 相似文献
236.
237.
In this study, poly(?-caprolactone)-based polyurethane (PCL-PU) nanofibers containing Ag nanoparticles for use in antimicrobial nanofilter applications were prepared by electrospinning 8 wt% PCL-PU solutions containing different amounts of AgNO3 in a mixed solvent consisting of DMF/THF (7/3 w/w). The average diameter of the pure PCL-PU nanofibers was 560 nm and decreased with increasing concentration of AgNO3. The PCL-PU nanofiber mats electrospun with AgNO3 exhibited higher tensile strength, tensile modulus, and lower elongation than the pure PCL-PU nanofiber mats. Small Ag nanoparticles were produced by the reduction of Ag+ ions in the PCL-PU solutions. The average size and number of the Ag nanoparticles in the PCL-PU nanofibers were considerably increased after being annealed at 100 °C for 24 h. They were all sphere-shaped and evenly distributed in the PCL-PU nanofibers, indicating that the PCL-PU chains stabilized the Ag nanoparticles well. 相似文献
238.
Solvignon P Liyanage N Chen JP Choi S Aniol K Averett T Boeglin W Camsonne A Cates GD Chang CC Chudakov E Craver B Cusanno F Deur A Dutta D Ent R Feuerbach R Frullani S Gao H Garibaldi F Gilman R Glashausser C Gorbenko V Hansen O Higinbotham DW Ibrahim H Jiang X Jones M Kelleher A Kelly J Keppel C Kim W Korsch W Kramer K Kumbartzki G Lerose JJ Lindgren R Ma B Margaziotis DJ Markowitz P McCormick K Meziani ZE Michaels R Moffit B Monaghan P Munoz Camacho C Paschke K Reitz B Saha A Sheyor R 《Physical review letters》2008,101(18):182502
We present experimental results of the first high-precision test of quark-hadron duality in the spin-structure function g_{1} of the neutron and 3He using a polarized 3He target in the four-momentum-transfer-squared range from 0.7 to 4.0 (GeV/c);{2}. Global duality is observed for the spin-structure function g_{1} down to at least Q;{2}=1.8 (GeV/c);{2} in both targets. We have also formed the photon-nucleon asymmetry A1 in the resonance region for 3He and found no strong Q2 dependence above 2.2 (GeV/c);{2}. 相似文献
239.
Wu W Kiryukhin V Noh HJ Ko KT Park JH Ratcliff W Sharma PA Harrison N Choi YJ Horibe Y Lee S Park S Yi HT Zhang CL Cheong SW 《Physical review letters》2008,101(13):137203
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. 相似文献
240.
Young-Ho Ko Min-Wook Oh Jae Ki Lee Su-Dong Park Kwang-Joo Kim Yoon-Soo Choi 《Current Applied Physics》2014,14(11):1538-1542
The crystal structure of AgSbTe2 has been refined using first-principles calculations, from which the ordering of the cations, Ag and Sb, was confirmed. The spontaneous formation of two (D4 and L11) phases at ambient and elevated pressure was demonstrated theoretically. The compound was also prepared and its high-pressure structural deformation sequence, ranging from ambient to 50.9 GPa, was observed with synchrotron radiation at room temperature. The compound underwent a pressure-induced amorphization (PIA) at 24.6 GPa and then started recrystallizing at 49.2 GPa. The bulk modulus (B0) and pressure derivative of the bulk modulus (Bp) were determined experimentally to be 56.3 ± 5.1 GPa and 4.3 ± 0.8, respectively. We suggest that large displacements of Te atoms to Ag vacancy positions are responsible for PIA and the recrystallization. 相似文献