※ 半角英数字
 年 ~ 
検索結果: 95 件中 1件目~20件目を表示


Initialising ...



Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...


Initialising ...



Evidence for strong correlations at finite temperatures in the dimerized magnet Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$

Shangguan, Y.*; Bao, S.*; Dong, Z.-Y.*; Cai, Z.*; Wang, W.*; Huang, Z.*; Ma, Z.*; Liao, J.*; Zhao, X.*; 梶本 亮一; et al.

Physical Review B, 104(22), p.224430_1 - 224430_8, 2021/12

Dimerized magnets forming alternating Heisenberg chains exhibit quantum coherence and entanglement and thus can find potential applications in quantum information and computation. However, magnetic systems typically undergo thermal decoherence at finite temperatures. Here, we show inelastic neutron scattering results on an alternating antiferromagnetic-ferromagnetic chain compound Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$ that the excited quasiparticles can counter thermal decoherence and maintain strong correlations at elevated temperatures. At low temperatures, we observe clear dispersive singlet-triplet excitations arising from the dimers formed along the crystalline $$b$$-axis. The excitation gap is of $$sim$$18 meV and the bandwidth is about half of the gap. The band top energy has a weak modulation along the [100] direction, indicative of a small interchain coupling. The gap increases while the bandwidth decreases with increasing temperature, leading to a strong reduction in the available phase space for the triplons. As a result, the Lorentzian-type energy broadening becomes highly asymmetric as the temperature is raised. These results are associated with a strongly correlated state resulting from hard-core constraint and quasiparticle interactions. We consider these results to be not only evidence for strong correlations at finite temperatures in Na$$_{2}$$Cu$$_{2}$$TeO$$_{6}$$, but also for the universality of the strongly correlated state in a broad range of quantum magnetic systems.


Atomic arrangements of quasicrystal bilayer graphene; Interlayer distance expansion

深谷 有喜; Zhao, Y.*; Kim, H.-W.*; Ahn, J.-R.*; 吹留 博一*; 松田 巌*

Physical Review B, 104(18), p.L180202_1 - L180202_5, 2021/11



Coordination number regulation of molybdenum single-atom nanozyme peroxidase-like specificity

Wang, Y.*; Jia, G.*; Cui, X.*; Zhao, X.*; Zhang, Q.*; Gu, L.*; Zheng, L.*; Li, L. H.*; Wu, Q.*; Singh, D. J.*; et al.

Chem, 7(2), p.436 - 449, 2021/02

 被引用回数:13 パーセンタイル:99.48(Chemistry, Multidisciplinary)

Nanozymes are promising alternatives to natural enzymes, but their use remains limited owing to poor specificity. Overcoming this is extremely challenging due to the intrinsic structural complexity of these systems. We report theoretical design and experimental realization of a series of heterogeneous molybdenum single-atom nanozymes (named Mo$$_{rm{SA}}$$-N$$_{x}$$-C), wherein we find that the peroxidase-like specificity is well regulated by the coordination numbers of single Mo sites. The resulting Mo$$_{rm{SA}}$$-N$$_{3}$$-C catalyst shows exclusive peroxidase-like behavior. It achieves this behavior via a homolytic pathway, whereas Mo$$_{rm{SA}}$$-N$$_{2}$$-C and Mo$$_{rm{SA}}$$-N$$_{4}$$-C catalysts have a different heterolytic pathway. The mechanism of this coordination-number-dependent enzymatic specificity is attributed to geometrical structure differences and orientation relationships of the frontier molecular orbitals.


Stacking fault driven phase transformation in CrCoNi medium entropy alloy

He, H.*; Naeem, M.*; Zhang, F.*; Zhao, Y.*; Harjo, S.; 川崎 卓郎; Wang, B.*; Wu, X.*; Lan, S.*; Wu, Z.*; et al.

Nano Letters, 21(3), p.1419 - 1426, 2021/02

 被引用回数:3 パーセンタイル:0(Chemistry, Multidisciplinary)

In CrCoNi, a so-called medium-entropy alloy, an fcc-to-hcp phase transformation has long been anticipated. Here, we report an in situ loading study with neutron diffraction, which revealed a bulk fcc-to-hcp phase transformation in CrCoNi at 15 K under tensile loading. By correlating deformation characteristics of the fcc phase with the development of the hcp phase, it is shown that the nucleation of the hcp phase was triggered by intrinsic stacking faults. The confirmation of a bulk phase transformation adds to the myriads of deformation mechanisms available in CrCoNi, which together underpin the unusually large ductility at low temperatures.


Ultralow thermal conductivity from transverse acoustic phonon suppression in distorted crystalline $$alpha$$-MgAgSb

Li, X.*; Liu, P.-F.*; Zhao, E.*; Zhang, Z.*; Guide, T.*; Le, M. D.*; Avdeev, M.*; 池田 一貴*; 大友 季哉*; 古府 麻衣子; et al.

Nature Communications (Internet), 11(1), p.942_1 - 942_9, 2020/02

 被引用回数:15 パーセンタイル:93.25(Multidisciplinary Sciences)



Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe$$_{2}$$Ge$$_{2}$$

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.

Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05

 被引用回数:2 パーセンタイル:35.62(Physics, Multidisciplinary)

We report neutron scattering measurements of single-crystalline YFe$$_{2}$$Ge$$_{2}$$ in the normal state, which has the same crystal structure as the 122 family of iron pnictide superconductors. YFe$$_{2}$$Ge$$_{2}$$ does not exhibit long-range magnetic order but exhibits strong spin fluctuations. Like the iron pnictides, YFe$$_{2}$$Ge$$_{2}$$ displays anisotropic stripe-type antiferromagnetic spin fluctuations at ($$pi, 0, pi$$). More interesting, however, is the observation of strong spin fluctuations at the in-plane ferromagnetic wave vector ($$0, 0, pi$$). These ferromagnetic spin fluctuations are isotropic in the ($$H, K$$) plane, whose intensity exceeds that of stripe spin fluctuations. Both the ferromagnetic and stripe spin fluctuations remain gapless down to the lowest measured energies. Our results naturally explain the absence of magnetic order in YFe$$_{2}$$Ge$$_{2}$$ and also imply that the ferromagnetic correlations may be a key ingredient for iron-based materials.


Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in BaFe$$_{2-x}$$T$$_{x}$$As$$_{2}$$ ($$T$$ = Co,Ni)

Tam, D. M.*; Song, Y.*; Man, H.*; Cheung, S. C.*; Yin, Z.*; Lu, X.*; Wang, W.*; Frandsen, B. A.*; Liu, L.*; Gong, Z.*; et al.

Physical Review B, 95(6), p.060505_1 - 060505_6, 2017/02

 被引用回数:18 パーセンタイル:75.96(Materials Science, Multidisciplinary)

We use neutron diffraction and muon spin relaxation to study the effect of in-plane uniaxial pressure on the antiferromagnetic (AF) orthorhombic phase in BaFe$$_{2-x}$$T$$_{x}$$As$$_{2}$$ and its Co- and Ni-substituted members near optimal superconductivity. In the low-temperature AF ordered state, uniaxial pressure necessary to detwin the orthorhombic crystals also increases the magnetic ordered moment, reaching an 11% increase under 40 MPa for BaFe$$_{1.9}$$Co$$_{0.1}$$As$$_2$$, and a 15% increase for BaFe$$_{1.915}$$Ni$$_{0.085}$$As$$_2$$. We also observe an increase of the AF ordering temperature ($$T_N$$) of about 0.25 K/MPa in all compounds, consistent with density functional theory calculations that reveal better Fermi surface nesting for itinerant electrons under uniaxial pressure. The doping dependence of the magnetic ordered moment is captured by combining dynamical mean field theory with density functional theory, suggesting that the pressure-induced moment increase near optimal superconductivity is closely related to quantum fluctuations and the nearby electronic nematic phase.


Spin excitations in optimally P-doped BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$ superconductor

Hu, D.*; Yin, Z.*; Zhang, W.*; Ewings, R. A.*; 池内 和彦*; 中村 充孝; Roessli, B.*; Wei, Y.*; Zhao, L.*; Chen, G.*; et al.

Physical Review B, 94(9), p.094504_1 - 094504_7, 2016/09


 被引用回数:14 パーセンタイル:64.66(Materials Science, Multidisciplinary)

最適Pドープされた超伝導体BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$ (T$$_c$$=30K)におけるスピン励起の温度及びエネルギー依存性が非弾性中性子散乱実験を使って調べられた。我々の実験結果は密度汎関数理論や動的平均場理論で予想される計算結果と矛盾しておらず、BaFe$$_2$$(As$$_{0.7}$$P$$_{0.3}$$)$$_2$$における平均プニクトゲン高さの減少が、電子相関の強さを弱め、磁気励起の有効バンド幅の増加に寄与することを示唆している。


Phase behavior and Li$$^{+}$$ ion conductivity of styrene-ethylene oxide multiblock copolymer electrolytes

Sarapas, J. M.*; 西条 賢次*; Zhao, Y.; 竹中 幹人*; Tew, G. N.*

Polymers for Advanced Technologies, 27(7), p.946 - 954, 2016/07

 被引用回数:8 パーセンタイル:38.84(Polymer Science)

A molecular weight series of PS-PEO multiblock copolymers was synthesized by the thiol-norbornene click reaction. These materials were characterized both as neat and lithium $$bis$$-trifluorosulfonimide salt loading samples. The neat samples demonstrated the crystallinity increases with PEO contents. The lithium ion-containing samples had broad scattering peaks, half of which displayed disordered scattering. Fitting of disordered scattering peaks by the random phase approximation, yielded the effective Flory-huggins parameter ($$chi$$$$_{RPA}$$) and radius of gyration ($$R$$$$_{g}$$) values that were compared to recent predictive works by Balsara and coworkers. The samples were also analyzed by electrochemical impedance spectroscopy for their potential to conduct lithium ions and those with the volume fraction of PEO larger than 0.5 demonstrated robust conductivity.


Elucidation of the morphology of the hydrocarbon multi-block copolymer electrolyte membranes for proton exchange fuel cells

Zhao, Y.; 吉田 実留*; 大島 竜也*; 小泉 智*; 陸川 政弘*; Szekely, N.*; Radulescu, A.*; Richter, D.*

Polymer, 86, p.157 - 167, 2016/03

 被引用回数:12 パーセンタイル:53.39(Polymer Science)

We investigated the structure and the swelling behavior of two synthesized hydrocarbon polymer electrolyte membranes, made of multiblock copolymer poly(sulphonate phenylene)-b-poly(arylene ether ketone) with different block ratios, by using small-angle neutron scattering technique. A scattering maximum (ionomer peak) at high-q range is shown commonly in both dry and wet states, with q being the magnitude of the scattering vector, while it shifts towards low-q region in the wet state due to the swelling of the ionomer domains with water. The swelling effect also results to a second scattering maximum in the middle-q range because of the water-induced microphase separation. The morphology in this q-range was elucidated in terms of Hard-Sphere model with Percus-Yervick interference approximation.


Dispersing zwitterions into comb polymers for nonviral transfection; Experiments and molecular simulation

Ghobadi, A. F.*; Letteri, R.*; Parelkar, S. S.*; Zhao, Y.; Chan-Seng, D.*; Emrick, T.*; Jayaraman, A.*

Biomacromolecules, 17(2), p.546 - 557, 2016/02

 被引用回数:10 パーセンタイル:46.63(Biochemistry & Molecular Biology)

We report the effect of embedding zwitterionic sulfobetaine (SB) groups in cationic comb polymers on polymer-DNA binding complexes (polyplexes), using a combination of experiments and molecular simulations. Ring-opening metathesis polymerization (ROMP) produced comb polymers with tetralysine (K4) and SB pendent groups. Dynamic light scattering, zeta potential measurements, and fluorescence-based experiments, together with coarse-grained molecular dynamics simulations, described the effect of SB groups on the size, shape, surface charge, composition, and DNA binding strength of polyplexes formed using these comb polymers. Experiments and simulations showed that increasing SB composition in the comb polymers decreased polymer-DNA binding strength, while the SB groups distributed throughout the polyplex. This allows polyplexes to maintain a positive surface charge and provide high levels of gene expression in live cells.


Imidazolium-based anion exchange membranes for alkaline anion fuel cells; Elucidation of the morphology and the interplay between the morphology and properties

Zhao, Y.; 吉村 公男; 猪谷 秀幸*; 山口 進*; 田中 裕久*; 小泉 智*; Szekely, N.*; Radulescu, A.*; Richter, D.*; 前川 康成

Soft Matter, 12(5), p.1567 - 1578, 2016/02

 被引用回数:23 パーセンタイル:82.25(Chemistry, Physical)

We investigated the interplay between morphology and properties of a new graft-type of anion exchange membranes (AEMs) containing 2-methylimidazolium groups by using contrast variation small angle neutron scattering (SANS) technique. These AEMs prepared by radiation-induced grafting of 2-methyl-1-vinylimidazole and styrene into poly(ethylene-co-tetrafluoroethylene) (ETFE) films, possessed both high alkaline durability and high conductivity. The SANS measurement reveals that these membranes are consisted of three phases: crystalline lamellar and crystallite domains originating from the pristine ETFE, which offer good mechanical properties, hydrophobic amorphous domains, which offer a matrix to create conducting regions, and interconnected hydrated domains, which are composed of the entire graft chains and water and play a key role to promote the conductivity.


A Crafty utilization of intermediate-angle neutron scattering and contrast variation by water-exchange to study the microstructure of microbial cellulose

Zhao, Y.; 小泉 智*; 近藤 哲男*

JPS Conference Proceedings (Internet), 8, p.033002_1 - 033002_6, 2015/09

Incoherent neutron scattering contribution presents a challenge in the structure characterization of many target materials. In this study, we introduce a method of intermediate angle neutron scattering (IANS) to correct the small angle neutron scattering (SANS) data of the water-swollen microbial cellulose (MC) sample, the system of which has significant incoherent contributions from the water solvent, and we describe the effects that the corrections have on the structural analysis. In order to elucidate the structure, the solvent is changed in situ from protonated water to deuterated water to give different scattering contrast, and this water-exchange process has been followed by time-resolved SANS and IANS simultaneously. Our results show that: (1) after incoherent correction, the structure of MC sample is proved to be invariant with solvents; (2) the scattering intensity depends only on the contrast factor, revealing a two-phase system composed of water-resistant crystalline cellulose phase and hydrated phase; (3) The cellulose crystallites have a constant scattering length density of 2.0$$times$$10$$^{10}$$cm$$^{-2}$$, determined by the matching point at which the scattering contrast between the two phases is minimum. This value is consistent with that of 1.9$$times$$10$$^{10}$$cm$$^{-2}$$ estimated from its chemical structure.


Combining small-angle and intermediate-angle neutron scattering to study the hierarchical structure in microbial cellulose

Zhao, Y.; 小泉 智

European Polymer Journal, 66, p.437 - 443, 2015/05

 被引用回数:2 パーセンタイル:8.84(Polymer Science)

In this study, we employed intermediate angle neutron scattering (IANS) technique to correct the small angle neutron scattering (SANS) data of the water-swollen microbial cellulose (MC) sample, the system of which has a significant incoherent contribution from the water solvent, and we described the effects that the corrections have on the structural analysis. In order to elucidate the structure efficiently, the solvent was exchanged in situ between protonated water and deuterated water to give different scattering contrasts, and the water-exchange processes were followed by time-resolved SANS and IANS simultaneously. Our results showed that: (1) after incoherent correction, the microstructure of MC sample was proved to be invariant with solvents; (2) the scattering intensity depended only on the contrast factor, revealing a two-phase system composed of waterresistant crystalline cellulose phase and hydrated amorphous phase; (3) the cellulosecrystallites have a constant scattering length density of 2.0$$times$$10$$^{10}$$ cm$$^{-2}$$, determined by the matching point at which the scattering contrast between the two phases is minimum. This value was consistent with that of 1.9$$times$$10$$^{10}$$ cm$$^{-2}$$ estimated from its chemical structure.


Coherent control of single spins in silicon carbide at room temperature

Widmann, M.*; Lee, S.-Y.*; Rendler, T.*; Son, N. T.*; Fedder, H.*; Paik, S.*; Yang, L.-P.*; Zhao, N.*; Yang, S.*; Booker, I.*; et al.

Nature Materials, 14(2), p.164 - 168, 2015/02

 被引用回数:309 パーセンタイル:99.49(Chemistry, Physical)

Single silicon vacancy (V$$_{Si}$$) in silicon carbide (SiC) was studied from the point of view of single photon source for quantum computing. The V$$_{Si}$$ centers were created in high purity semi-insulating hexagonal (4H)-SiC by 2 MeV electron irradiation with fluences up to 5$$times$$10$$^{15}$$ /cm$$^{2}$$. No subsequent annealing was carried out. A couple of solid immersion lens (SIL) with 20 $$mu$$m diameter were created on samples by ion milling using 40 keV Ga focused ion beam. A typical home-built confocal setup was used after optimizing for emission in the wavelength range around 900 nm. As a result, optically detected electron spin resonance (ODMR) for V$$_{Si}$$ was observed at room temperature (RT). Using ODMR, Rabi oscillations were also observed, and the Rabi frequency increased with increasing applied-magnetic field. In addition, spin relaxation time T$$_{1}$$ and T$$_{2}$$ were detected to be 500 $$mu$$s and 160 $$mu$$s, respectively.


Hierarchical structure in microbial cellulose; What happens during the drying process

Zhao, Y.; 小泉 智; 山口 大輔; 近藤 哲男*

European Physical Journal E, 37(12), p.129_1 - 129_12, 2014/12

 被引用回数:7 パーセンタイル:36.01(Chemistry, Physical)

We present a time-resolved investigation of the natural drying process of microbial cellulose (MC) by means of simultaneous small-angle neutron scattering (SANS), intermediate-angle neutron scattering (IANS) and weighing techniques. SANS was used to elucidate the microscopic structure of the MC sample. The coherent scattering length density of the water penetrating amorphous domains varied with time during the drying process to give a tunable scattering contrast to the water-resistant cellulose crystallites, thus the contrast variation was automatically performed by simply drying.


Diluted ferromagnetic semiconductor Li(Zn,Mn)P with decoupled charge and spin doping

Deng, Z.*; Zhao, K.*; Gu, B.; Han, W.*; Zhu, J. L.*; Wang, X. C.*; Li, X.*; Liu, Q. Q.*; Yu, R. C.*; 後神 達郎*; et al.

Physical Review B, 88(8), p.081203_1 - 081203_5, 2013/08

 被引用回数:66 パーセンタイル:92.87(Materials Science, Multidisciplinary)

We report the discovery of a diluted magnetic semiconductor, Li(Zn,Mn)P, in which charge and spin are introduced independently via lithium off-stoichiometry and the isovalent substitution of Mn$$^{2+}$$ for Zn$$^{2+}$$, respectively. Isostructural to (Ga,Mn)As, Li(Zn,Mn)P was found to be a ${it p}$-type ferromagnetic semiconductor with excess lithium providing charge doping. First-principles calculations indicate that excess Li is favored to partially occupy the Zn site, leading to hole doping. Ferromagnetism with Curie temperature up to 34 K is achieved while the system still shows semiconducting transport behavior.


Anisotropic two-dimensional electron gas at the LaAlO$$_{3}$$/SrTiO$$_{3}$$ (110) interface

Annadi, A.*; Zhang, Q.*; Renshaw Wang, X.*; Tuzla, N.*; Gopinadhan, K.*; L$"u$, W. M.*; Roy Barman, A.*; Liu, Z. Q.*; Srivastava, A.*; Saha, S.*; et al.

Nature Communications (Internet), 4, p.1838_1 - 1838_7, 2013/05

 被引用回数:84 パーセンタイル:94.96(Multidisciplinary Sciences)

We report the observation of unexpected conductivity at the LaAlO$$_{3}$$/SrTiO$$_{3}$$ interface prepared on (110)-oriented SrTiO$$_{3}$$, with a LaAlO$$_{3}$$-layer thickness-dependent metal-insulator transition. Density functional theory calculation reveals that electronic reconstruction, and thus conductivity, is still possible at this (110) interface by considering the energetically favourable (110) interface structure, that is, buckled TiO$$_{2}$$/LaO, in which the polarization discontinuity is still present. The conductivity was further found to be strongly anisotropic along the different crystallographic directions with potential for anisotropic superconductivity and magnetism, leading to possible new physics and applications.


Signature splitting inversion and backbending in $$^{80}$$Rb

He, C.*; Shen, S.*; Wen, S.*; Zhu, L.*; Wu, X.*; Li, G.*; Zhao, Y.*; Yan, Y.*; Bai, Z.*; Wu, Y.*; et al.

Physical Review C, 87(3), p.034320_1 - 034320_10, 2013/03

 被引用回数:5 パーセンタイル:42.24(Physics, Nuclear)

High-spin states of $$^{80}$$Rb are studied via the fusion-evaporation reactions $$^{65}$$Cu+$$^{19}$$F, $$^{66}$$Zn+$$^{18}$$O, and $$^{68}$$Zn+$$^{16}$$O with the beam energies of 75 MeV, 76 MeV, and 80 MeV, respectively. Twenty-three states with twenty-eight $$gamma$$ transitions are added to the previously proposed level scheme, where the second negative-parity band is significantly pushed up to spins of 22$$^-$$ and 15$$^-$$ and two sidebands are built on the known first negative-parity band. Two successive band crossings with frequencies 0.51 MeV and 0.61 MeV in the $$alpha$$ = 0 branch as well as another one in the $$alpha$$ =1 branch of the second negative-parity band are observed. Signature inversions occur in the positive-parity and first negative-parity bands at the spins of 11$$hbar$$ and 16$$hbar$$, respectively. The signature splitting is seen obviously in the second negative-parity band, but the signature inversion is not observed. It is also found that the structure of the two negative-parity bands is similar to that of its isotone $$^{82}$$Y. Signature inversion in the positive-parity yrast band with configuration $$pi$$g9/2 $$otimes$$ $$nu$$g9/2 in this nucleus is discussed using the projected shell model.


Order-disorder transition of nanocomposites; Polystyrene-$$block$$-poly(methyl methacrylate) with Pd nanoparticles

Zhao, Y.; 西条 賢次*; 橋本 竹治

Macromolecules, 46(3), p.957 - 970, 2013/02

 被引用回数:7 パーセンタイル:26.96(Polymer Science)

We studied how the palladium nanoparticles, (Pd)$$_{n}$$s, incorporated into poly(styrene)-$$block$$-poly(methyl methacylate) (PS-$$b$$-PMMA) block copolymer (bcp), alter its order-disorder transition (ODT). The (Pd)$$_{n}$$s were incorporated into the lamellar template of PS-$$b$$-PMMA by the thermal reduction of palladium acetylacetonate, dissolved uniformly in the bcp in the disordered state. The ODT behavior of the neat bcp and the nanocomposites are investigated by small angle X-ray scattering as a function of temperature. We found the incorporation of a very small amount of (Pd)$$_{n}$$s significantly increased the ODT temperature by about 8$$^{circ}$$C, which is due to the stronger attractive interactions of (Pd)$$_{n}$$s with PS block chains than with PMMA block chains, which increases the net effective segregation power between PS and PMMA block chains and hence stabilizes the ordered lamellae.

95 件中 1件目~20件目を表示