排序方式: 共有31条查询结果,搜索用时 15 毫秒
1.
Cai YQ Chow PC Restrepo OD Takano Y Togano K Kito H Ishii H Chen CC Liang KS Chen CT Tsuda S Shin S Kao CC Ku W Eguiluz AG 《Physical review letters》2006,97(17):176402
A sharp feature in the charge-density excitation spectra of single-crystal MgB2, displaying a remarkable cosinelike, periodic energy dispersion with momentum transfer (q) along the c* axis, has been observed for the first time by high-resolution nonresonant inelastic x-ray scattering (NIXS). Time-dependent density-functional theory calculations show that the physics underlying the NIXS data is strong coupling between single-particle and collective degrees of freedom, mediated by large crystal local-field effects. As a result, the small-q collective mode residing in the single-particle excitation gap of the B pi bands reappears periodically in higher Brillouin zones. The NIXS data thus embody a novel signature of the layered electronic structure of MgB2. 相似文献
2.
Y. Kondo T. Nakamura Y. Satou T. Matsumoto N. Aoi N. Endo N. Fukuda T. Gomi Y. Hashimoto M. Ishihara S. Kawai M. Kitayama T. Kobayashi Y. Matsuda N. Matsui T. Motobayashi T. Nakabayashi T. Okumura H.J. Ong T.K. Onishi K. Ogata H. Otsu H. Sakurai S. Shimoura M. Shinohara T. Sugimoto S. Takeuchi M. Tamaki Y. Togano Y. Yanagisawa 《Physics letters. [Part B]》2010
3.
K. Tshoo Y. Satou H. Bhang S. Choi T. Nakamura S. Deguchi Y. Kawada Y. Kondo N. Kobayashi Y. Nakayama K. N. Tanaka N. Tanaka N. Aoi M. Ishihara T. Motobayashi H. Otsu H. Sakurai S. Takeuchi Y. Togano K. Yoneda Z. H. Li F. Delaunay J. Gibelin F. M. Marques N. A. Orr T. Honda M. Matsushita T. Kobayashi Y. Miyashita T. Sumikama K. Yoshinaga S. Shimoura D. Sohler T. Zheng Z.X. Cao 《Few-Body Systems》2013,54(1-4):459-463
The unbound excited states of the most neutron-rich dripline oxygen isotope, 24O, have been investigated by using the 24O(p,p′)24O* reaction at the beam energy of 62 MeV/nucleon in inverse kinematics. The first and second unbound excited states of 24O have been observed at ${E_{\rm x}= 4.63_{-0.14}^{+0.30}}$ MeV and ${E_{\rm x}= 5.13_{-0.24}^{+0.19}}$ MeV (preliminary) along with the evidence for another higher lying state at around 7.3 MeV. The quadrupole deformation parameter ${\beta_{2^+}}$ was deduced to be ${0.15_{-0.03}^{+0.08}}$ (preliminary) for the first time. The systematics of the ${\beta_{2^+}}$ and the ${E_{\rm x}(2_1^+)}$ in the Z = 8 isotopes shows the N = 16 spherical shell closure in 24O. 相似文献
4.
H. Kitaguchi K. Itoh T. Takeuchi H. Kumakura H. Miao H. Wada K. Togano T. Hasegawa T. Koizumi 《Physica C: Superconductivity and its Applications》1999,320(3-4):253-258
High-transport critical current density (Jc-oxide)>500 kA/cm2 at 4.2 K, 10 T can be obtained for Bi-2212/Ag tapes fabricated by using pre-annealing and intermediate rolling (PAIR) and melt-solidification process. In this paper, we report high-temperature properties of PAIR-processed Bi-2212/Ag multilayer tape in order to show their potential for practical applications operated at cryocooling temperatures. Magnetic field dependence and angular dependence of critical current (Ic) are investigated at temperatures ranging 10–50 K by using helium gas cooling and liquid neon. Field-temperature curves for Ic=0.2 and 2.0 A are also determined in order to show the approximation of the irreversible field. High-temperature performance of the tape is attractive to consider future applications. For example, the best sample carries Ic=267 A (engineering-Jc=303 A/mm2, Jc-oxide=151 kA/cm2) and 92 A (104 A/mm2, 52 kA/cm2) at 27.1 K (in liquid neon), in magnetic fields (parallel to the tape surface) of 2 and 10 T, respectively. Engineering-Jc of 100 A/mm2 is obtained even in the perpendicular field of 0.5 T at 27.1 K. 相似文献
5.
Soon after the discovery of Fe based superconductors, attempts of wire fabrication started using a powder-in-tube (PIT) technique, because their high transition temperature and extremely high upper critical field bring the hope of high field applications. Although the transport critical current density, , reported in the early stage was disappointingly low, it has been rapidly improved during the past one year to the orders of and 105 A/cm2 by optimizing various processing parameters of the PIT technique. This paper reports one of the works which brought such rapid progress. (Ba,K)Fe2As2 superconducting wires were fabricated by an ex situ powder-in-tube (PIT) process using a melt processed precursor material. The paper also discusses the influence of Ag addition, critical current irreversibility, critical current anisotropy of the tape sample, and finally future prospect in the development of Fe based superconducting wires. 相似文献
6.
J.W. Ekin T.M. Larson A.M. Hermann Z.Z. Sheng K. Togano H. Kumakura 《Physica C: Superconductivity and its Applications》1989,160(5-6):489-496
A double step characteristic is observed at 76 K in the transport critical current as a function of magnetic field (10-4 T to 10 T) in bulk sintered Y-, Bi- and Tl-based high-Tc superconducting materials. The low-field, step-like drop in the critical current density Jc commences at magnetic fields B between about 0.3 and 2 mT. This is followed by a plateau region of relatively constant critical current extending from about 30 to 300 mT, and then a second drop at fields between about 0.3 and 10 T. These features occur for all three superconductor materials and are interpreted respectively as a self-field/weak-link regime, a remnant percolation path regime and a flux-flow/upper-critical-field regime. The sharpness of the transition of the voltage-current (V-I characteristic, represented by the transition parameter n (i.e., V∝In), has a similar double-step shape as a function of magnetic field directly corresponding to the features of the Jc(B) characteristic. 相似文献
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8.
Metastable A-15 and amorphous phases have been prepared in liquid-quenched Nb-Si binary alloys. The results suggest that the presence of interstitial impurities has a stabilizing influence on the A-15 structure. 相似文献
9.
T. Yamaguchi K. TanakaT. Suzuki A. OzawaT. Ohtsubo T. AibaN. Aoi H. BabaM. Fukuda Y. HashizumeK. Inafuku N. IwasaT. Izumikawa K. KobayashiM. Komuro Y. KondoT. Kubo M. KurokawaT. Matsuyama S. Michimasa T. MotobayashiT. Nakabayashi S. NakajimaT. Nakamura H. SakuraiR. Shinoda M. ShinoharaH. Suzuki M. TakechiE. Takeshita S. TakeuchiY. Togano K. YamadaT. Yasuno M. Yoshitake 《Nuclear Physics A》2011,864(1):1-37
Reaction cross sections with various kinds of breakup channels for neutron-rich carbon isotopes 18-20C and for 9Be impinging on a liquid hydrogen target were investigated at 40 MeV/nucleon. The nuclides of interest were produced via projectile fragmentation from a 63 MeV/nucleon 40Ar beam and were separated in flight at the RIKEN projectile fragment separator (RIPS). The combination of the large-acceptance superconducting TOF spectrometer, TOMBEE (TOF Mass analyzer for exotic BEam Experiment), with a liquid hydrogen target, CRYPTA (CRYogenic ProTon and Alpha target system), enables simultaneous measurements of several reaction channels: the reaction cross sections (σR), individual elemental fragmentation cross sections (σΔZ), charge-changing cross sections (σcc), neutron-removal cross sections (σ−xn), and charge-pickup cross sections (σΔZ+1) for 19,20C; σΔZ, σ−xn, and σΔZ+1 for 18C; and σR for 9Be. The present σR of 9Be on proton, σR=397±23 mb, measured in the inverse kinematics, was consistent with the previous measurements using proton beams at different laboratories. The σR of 19C and 20C on proton were determined to be σR=754±22 mb and σR=791±34 mb, respectively. Taking into account the beam energy and target dependence of σR, the present σR are found to be considerably enhanced compared with those measured at around 1 GeV/nucleon. The σΔZ+1 appears to increase with the mass number of the projectiles, and it significantly contributes to σR in the present energy range. The finite-range optical-limit and few-body Glauber model analyses were performed for σR to study the nuclear matter density distributions and to derive the relative strength of the s-wave components of the valence neutrons in 19C and 20C. A neutron halo structure of 19C is confirmed with an s-wave dominance of the valence neutron when the effect of the charge-pickup reaction is taken into account. The large σ−n of 19C and σ−2n of 20C also support the decoupled structures of 18C +n and 18C+2n, respectively. The σcc of 19C and 20C agree with each other within their experimental uncertainties, which might indicate a similar proton density distribution in 19C and 20C. The σΔZ decreases monotonically without the even-odd effect as the number of removed protons increases. 相似文献
10.
J. W. Hwang Y. Satou T. Nakamura Y. Kondo N. Matsui Y. Hashimoto T. Nakabayashi T. Okumura M. Shinohara N. Fukuda T. Sugimoto H. Otsu Y. Togano T. Motobayashi H. Sakurai Y. Yanagisawa N. Aoi S. Takeuchi T. Gomi M. Ishihara S. Kawai H. J. Ong T. K. Onishi S. Shimoura M. Tamaki T. Kobayashi Y. Matsuda N. Endo M. Kitayama 《Few-Body Systems》2013,54(7-10):1469-1472
The 16C nucleus has been investigated by the neutron knockout reaction of 17C on a liquid hydrogen target. Applying the invariant mass method in inverse kinematics and γ-ray spectroscopy, the energy spectrum was reconstructed by triple-coincidence measurement, in which neutrons, charged fragments, and γ rays from the decay of the reaction residue (16C*) were detected. A peak at 0.47 MeV was observed in the invariant mass spectrum in coincidence with a peak at 0.74 MeV in the γ-ray spectrum, which indicates the presence of an unbound state with an excitation energy of 5.46 MeV. Comparison of the experimental cross section with the value derived by a theoretical calculation provided evidence that the spin-parity of this state is 2?. 相似文献