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Elyasi, M.*; 山本 慧; 日置 友智*; 巻内 崇彦*; 清水 祐樹*; 齊藤 英治*; Bauer, G. E. W.*
Physical Review B, 109(18), p.L180402_1 - L180402_7, 2024/05
Magnets are interesting materials for classical and quantum information technologies. However, the short decoherence and dephasing times that determine the scale and speed of information networks severely limit the appeal of employing the ferromagnetic resonance. Here we show that the lifetime and coherence of the uniform Kittel mode can be enhanced by three-magnon interaction-induced mixing with the long-lived magnons at the minima of the dispersion relation. Analytical and numerical calculations based on this model explain recent experimental results and predict experimental signatures of quantum coherence.
静間 俊行*; Omer, M.; 羽島 良一*; 小泉 光生
Physical Review C, 109(5), p.054320_1 - 054320_8, 2024/05
Low-lying levels in the odd-mass nucleus Ta have been populated via nuclear resonance fluorescence using a quasi-monoenergetic, linearly polarized photon beam at the High Intensity -ray Source (HIS) facility at Duke University. The spin and parity of the levels were determined from the azimuthal intensity asymmetry of resonantly scattered -rays with respect to the polarization plane of the incident photon beam. The electric and magnetic dipole strengths were obtained for excitation energies from 2.2 to 3.2 MeV. The results are discussed in terms of the nuclear scissors mode. This work is a contribution of the Japan Atomic Energy Agency (JAEA) to the International Atomic Energy Agency (IAEA) under the agreement of the coordinated research program (CRP), J02015 (Facilitation of Safe and Secure Trade Using Nuclear Detection Technology - Detection of RN and Other Contraband). This work was a part of a study of the nuclear resonance fluorescence aiming at nuclear security and safeguards applications, being supported by the subsidiary for "promotion of strengthening nuclear security or the like" of the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan.
岩元 大樹; 明午 伸一郎; 杉原 健太*
Physical Review C, 109(5), p.054610_1 - 054610_12, 2024/05
核種生成断面積は、原子力の研究、開発、宇宙探査、天体物理学的調査において極めて重要である。その重要性にもかかわらず、利用可能な実験データが限られているため、現象論的アプローチによる包括的な断面積推定の実用性が制限されている。この問題を解決するために、われわれは、豊富なデータを持つ元素の知識を、実験データが限られている、あるいは全くない元素に伝達することができるガウス過程に基づく機械学習(ML)モデルを提案する。われわれのMLモデルは、様々な元素の包括的な断面積推定を可能にするだけでなく、学習データが乏しい領域においても、物理モデルに近い予測能力を示す。
櫻井 敬久*; 紅林 泰*; 鈴木 颯一郎*; 堀内 一穂*; 高橋 唯*; 堂下 典弘*; 菊地 聡*; 門叶 冬樹*; 岩田 尚能*; 田島 靖*; et al.
Physical Review D, 109(10), p.102005_1 - 102005_18, 2024/05
銀河宇宙線の永年変化は銀河の活動に密接に関係しており、局所的な銀河磁場・星間雲・超新星残骸の近くの環境が反映される。高エネルギー銀河宇宙線によって大気中で生成される高エネルギーミューオンは、深い地層まで透過し、岩石中に放射性同位体を生成する。BeやAlのような長寿命の放射性核種は岩石中に蓄積されるため、高エネルギーミューオンの収量の長期変動、ひいては数百万年間の高エネルギー銀河宇宙線(GCR)の長期変動の調査に利用できる。本研究では、CERN SPSのCOMPASS実験ラインにて、160GeV/cの正ミューオンを合成石英プレートと花崗岩コアに照射して、岩石中のBeとAlの生成断面積を測定した。更に、ミューオンが直接起こす核破砕反応とミューオンが生成した二次粒子が引き起こす反応が、岩石中での長寿命核種の生成にそれぞれどの程度寄与するかを明らかにした。
奥平 琢也*; 中部 倫太郎*; Auton, C. J.*; 遠藤 駿典; 藤岡 宏之*; Gudkov, V.*; 井出 郁央*; 猪野 隆*; 石角 元志*; 神原 理*; et al.
Physical Review C, 109(4), p.044606_1 - 044606_9, 2024/04
We measured the spin dependence in a neutron-induced p-wave resonance by using a polarized epithermal neutron beam and a polarized nuclear target. Our study focuses on the 0.75 eV -wave resonance state of La+n, where largely enhanced parity violation has been observed. We determined the partial neutron width of the -wave resonance by measuring the spin dependence of the neutron absorption cross section between polarized La and polarized neutrons. Our findings serve as a foundation for the quantitative study of the enhancement effect of the discrete symmetry violations caused by mixing between partial amplitudes in the compound nuclei.
中部 倫太郎*; Auton, C. J.*; 遠藤 駿典; 藤岡 宏之*; Gudkov, V.*; 広田 克也*; 井出 郁央*; 猪野 隆*; 石角 元志*; 神原 理*; et al.
Physical Review C, 109(4), p.L041602_1 - L041602_4, 2024/04
Neutron transmission experiments can offer a new type of highly sensitive search for time-reversal invariance violating (TRIV) effects in nucleon-nucleon interactions via the same enhancement mechanism observed for large parity violating (PV) effects in neutron-induced compound nuclear processes. In these compound processes, the TRIV cross-section is given as the product of the PV cross-section, a spin-factor , and a ratio of TRIV and PV matrix elements. We determined to be 0.59 0.05 for La+n using both (n, ) spectroscopy and (+) transmission. This result quantifies for the first time the high sensitivity of the La 0.75 eV -wave resonance in a future search for -odd/-odd interactions in (+) forward transmission.
Filipescu, D.*; Gheorghe, I.*; Goriely, S.*; 西尾 勝久; 宇都宮 弘章*; 洲嵜 ふみ; 廣瀬 健太郎; 他10名*
Physical Review C, 109(4), p.044602_1 - 044602_23, 2024/04
New measurements of photofission and photoneutron reactions on U and Th in the Giant Dipole Resonance (GDR) energy region have been performed at the laser Compton-scattering -ray source of the NewSUBARU synchrotron radiation facility. The photoneutron () with = 1-3 and photofission () reactions have been discriminated by considering a Gaussian distribution of prompt-fission-neutron (PFN) multiplicities predicted by the theory of evaporation in sequential neutron emission from excited fission fragments. We report experimental (), (), () and () cross sections, average energies of PFNs and of(, ) photoneutrons, as well as the mean number of PFNs per fission and the width of the PFNs multiplicity distribution. Based on these primary experimental results and combined with reasonable assumptions, we extract also the first- and second-chance fission contributions.
山崎 匠*; 平井 孝昌*; 八木 貴志*; 山下 雄一郎*; 内田 健一*; 関 剛斎*; 高梨 弘毅
Physical Review Applied (Internet), 21(2), p.024039_1 - 024039_11, 2024/02
被引用回数:0 パーセンタイル:0.01(Physics, Applied)This study presents a measurement method for determining the figure of merit for transverse thermoelectric conversion in thin-film forms. Leveraging the proposed methodology, we comprehensively investigate the transverse thermoelectric coefficient, in-plane electrical conductivity, and out-of-plane thermal conductivity in epitaxial and polycrystalline Fe/Pt metallic multilayers.
Park, P.*; Cho, W.*; Kim, C.*; An, Y.*; Avdeev, M.*; 飯田 一樹*; 梶本 亮一; Park, J.-G.*
Physical Review B, 109(6), p.L060403_1 - L060403_7, 2024/02
Spontaneous Hall conductivity has recently been reported in the triangular lattice antiferromagnet CoTaS under a zero magnetic field. This phenomenon originates from the distinctive noncoplanar triple- magnetic ground state, possessing uniform real-space Berry curvature characterized by scalar spin chirality. We investigated the physical properties of CoTaS by judiciously controlling the composition, revealing a drastic change in its bulk properties, even by slight variations in cobalt composition, despite the same crystal structure. For , CoTaS keeps all the characteristics of the ground state consistent with the previous studies --- two antiferromagnetic phase transitions at and (), a large spontaneous Hall conductivity [], and a weak ferromagnetic moment along the axis. However, samples with exhibit distinct bulk properties, including the absence of both and the weak ferromagnetic moment. Our neutron diffraction data reveal that CoTaS with develops coplanar helical magnetic order with . This is entirely different from what has been seen in , explaining the observed composition dependence.
志賀 基之; Thomsen, B.; 君塚 肇*
Physical Review B, 109(5), p.054303_1 - 054303_12, 2024/02
パラジウム中の水素の中性子非弾性散乱スペクトルを有限温度での核量子効果を考慮して計算した。経路積分に基づく半古典分子動力学と機械学習ポテンシャルを組合せた計算手法を用いた。計算されたスペクトルは、水素原子の振動励起の基本波と第一高調波に対応するピークの位置と強度に関して、実験スペクトルとよく一致した。古典分子動力学法との比較から、中性子非弾性散乱スペクトルにおいて核量子効果が本質的な役割を果たしていることが示された。
山内 宏樹; Sari, D. P.*; 安井 幸夫*; 坂倉 輝俊*; 木村 宏之*; 中尾 朗子*; 大原 高志; 本田 孝志*; 樹神 克明; 井川 直樹; et al.
Physical Review Research (Internet), 6(1), p.013144_1 - 013144_9, 2024/02
-Mn-type family alloys Mn have three-dimensional antiferromagnetic (AFM) corner-shared triangular network. The antiferromagnet MnRhSi shows magnetic short-range order (SRO) over a wide temperature range of approximately 500 K above the Nel temperature = 190 K. MnCoSi has the smallest lattice parameter and the lowest in the family compounds. The quantum critical point (QCP) from AFM to the quantum paramagnetic state is expected near a cubic lattice parameter of 6.15 of MnCoSi is only 140 K, quantum critical behavior is observed in MnCoSi as the enhancement of the electronic specific heat coefficient . We study how the magnetic SRO appears in MnCoSi by using neutron scattering, SR, and physical property measurements. The experimental results show that the neutron scattering intensity of the magnetic SRO does not change much regardless of the suppressed magnetic moment in the long-range magnetic ordered state compared to those of MnRhSi. The initial asymmetry drop ratio of SR above becomes small, and the magnetic SRO temperature is suppressed to 240 K. The results suggest that the MnCoSi is close to the QCP in the Mn system.
菖蒲田 義博
Physical Review Accelerators and Beams (Internet), 27(1), p.011001_1 - 011001_25, 2024/01
被引用回数:0 パーセンタイル:0.19(Physics, Nuclear)円筒チャンバー内でバンチされた相対論的なビームの空間電荷チューンシフトを計算する際、一般に、チャンバー壁の代わりにコースティングビームに対する鏡像電流が使用される。そして、バンチ長を特徴付けるためにバンチ因子が直感的に導入される。そのため、この手法の妥当性はいまだ未確立である。本研究では、グリーン関数を用いてバンチされたビームの空間電荷チューンシフトの計算を行い、鏡像電流を使用して導出された以前の公式と比較する。
Huang, Z.*; Wang, W.*; Ye, H.*; Bao, S.*; Shangguan, Y.*; Liao, J.*; Cao, S.*; 梶本 亮一; 池内 和彦*; Deng, G.*; et al.
Physical Review B, 109(1), p.014434_1 - 014434_9, 2024/01
被引用回数:0 パーセンタイル:0.01(Materials Science, Multidisciplinary)TbMnSn is a correlated topological magnet with a Mn-based kagome lattice, in which a Chern gap opens at the Dirac point at low temperatures. The magnetic moment direction of the ferrimagnetic order changes from in the kagome plane to the out-of-plane upon cooling, which is essential for generating the Chern gap, but the underlying mechanism for the spin reorientation remains elusive. Here, we investigate the spin-reorientation transition in TbMnSn using neutron scattering. We provide direct evidence for the spin-reorientation transition and unveil the coexistence of two Tb modes at 200 K. To account for these results, we put forward a model based on SU(N) spin-wave theory, in which there is a temperature evolution of the ground state Tb orbitals, driven by the crystalline electric field, single-ion anisotropy, and exchange interactions between Tb and Mn ions. Our findings shed light on the complex magnetism of TbMnSn, despite its relatively simple ground state magnetic structure, and provide insights into the mechanisms for tuning magnetic topological materials.
静間 俊行*; Omer, M.; 早川 岳人*; 湊 太志*; 松葉 俊哉*; 宮本 修治*; 清水 則孝*; 宇都野 穣
Physical Review C, 109(1), p.014302_1 - 014302_7, 2024/01
被引用回数:0 パーセンタイル:0.19(Physics, Nuclear)Low-lying dipole states in the singly closed-shell nucleus Ni were studied via nuclear resonance fluorescence experiments using a quasi-monoenergetic, linearly polarized photon beam. The parity quantum numbers of the dipole states were determined by the intensity asymmetry of resonantly scattered -rays with respect to the polarization plane of the incident photon beam. The electric and magnetic dipole (E1 and M1) strengths at excitation energies between 5.9 and 9.8 MeV were obtained based on dipole strengths taken from literature. The E1 and M1 strength distributions were compared with large-scale shell-model predictions in the -shell using the SDPFSDG-MU interaction.
Ajayi, S.*; Tripathi, V.*; Rubino, E.*; Bhattacharya, S.*; Baby, L. T.*; Lubna, R. S.*; Benetti, C.*; Wibisono, C.*; Wheeler, M. B.*; Tabor, S. L.*; et al.
Physical Review C, 109(1), p.014305_1 - 014305_21, 2024/01
被引用回数:0 パーセンタイル:0.19(Physics, Nuclear)フロリダ州立大学のタンデム加速器にてCo, NiとCoの励起状態を生成し、そこからの脱励起ガンマ線からエネルギー準位を得た。Coについてはまでの、Niについてはまでの高スピン状態が得られた。これらの結果を殻から-軌道に1個までの励起を許す大規模殻模型計算と比較した結果、スピンがかなり大きなもの以外のイラスト状態の励起エネルギーをよく再現した。再現できなかった高スピン状態は、多粒子多空孔励起が主であると考えられる。また、殻模型計算からは、これらの高スピン状態のいくつかは遷移強度が強いバンドと考えられる。
宇都宮 弘章*; Goriely, S.*; 木村 真明*; 清水 則孝*; 宇都野 穣; Tveten, G. M.*; Renstrm, T.*; 有泉 高志*; 宮本 修治*
Physical Review C, 109(1), p.014617_1 - 014617_7, 2024/01
被引用回数:0ニュースバルのレーザー逆コンプトン散乱光を使って、Cの光中性子放出断面積を測定した。これまで実験的な不定性が大きかった、巨大共鳴の裾にあたるエネルギー領域にピーク構造があることを確認した。その結果を大規模殻模型計算、反対称化分子動力学計算と比較し、このピーク構造を含む、光核反応断面積をよく再現することがわかった。
Patel, D.*; Srivastava, P. C.*; 清水 則孝*; 宇都野 穣
Physical Review C, 109(1), p.014310_1 - 014310_16, 2024/01
被引用回数:0 パーセンタイル:0.19(Physics, Nuclear)大規模殻模型計算を使って、Cdの奇核のエネルギー準位とInで知られている核異性体を計算した。知られている準位構造をよく再現した。さらに、Cd同位体において系統的に測定されている、状態の電気的四重極モーメントに着目し、その中性子数に対する変化を調べた。これまでは、対相関が強い極限でよいとされる、セニョリティ描像によってこれらの四重極モーメントの値の変化が理解されてきた。大規模殻模型計算の結果、セニョリティ量子数はよくなく、変形が発達していることがわかった。四重極モーメントの変化は変形した原子核の回転軸方向を特徴づける量子数の変化によって理解されるという新しい描像を提示した。
古府 麻衣子; 河村 聖子; 村井 直樹; 石井 梨恵子*; 平井 大悟郎*; 有馬 寛*; 舟越 賢一*
Physical Review Research (Internet), 6(1), p.013006_1 - 013006_9, 2024/01
We revisited spin dynamics in archetypical classical spin glass systems, such as CuMn (, 0.034, and 0.067) dilute alloys and iron aluminosilicate glass using a modern neutron scattering spectrometer with high neutron flux. The former is crystalline, and the latter is amorphous, where their spin glass state is well separated from magnetically ordered phases. Bose-scaled localized magnetic excitations were observed in both compounds below the spin-freezing temperature (). The spectrum exhibits a maximum at low energy and a broad tail on the high-energy side. The excitation energy tends to be higher for the material with a higher . Above the , the spectrum considerably changes with temperature, thereby indicating the emergence of the magnetic relaxation process. The magnetic excitation in the spin glass state has much in common with the boson peak in structural glasses. We consider that the Bose-scaled broad excitation peak is an elementary excitation inherent in disordered systems.
角田 一樹; 藤田 裕一*; Zhou, W.*; 増田 啓介*; 川崎 郁斗; 藤森 伸一; 木村 昭夫*; 桜庭 裕弥*
Physical Review B, 108(24), p.L241101_1 - L241101_6, 2023/12
We investigated the element-specific electronic structure of a half-metallic Weyl ferromagnet candidate CoFeSi film by utilizing soft-X-ray resonant photoelectron spectroscopy and first-principles calculations with/without considering on-site Coulomb interaction. Fe 2-3 resonant photoelectron experiment revealed that the Fe 3 states exist around 2 and 4 eV below the Fermi energy. Our calculations, based on the generalized gradient approximation without considering Coulomb interaction at the Fe site, successfully reproduced the experimentally observed Fe 3 partial density of states. Our findings shed light on the highly controversial correlation effect of CoFeSi, offering valuable insights into its half-metallicity and Weyl semi-metallicity.
伊藤 孝; 髭本 亘; 下村 浩一郎*
Physical Review B, 108(22), p.224301_1 - 224301_11, 2023/12
被引用回数:1 パーセンタイル:0(Materials Science, Multidisciplinary)In positive muon spin rotation and relaxation (SR) spectroscopy, positive muons () implanted into solid oxides are conventionally treated as immobile spin-probes at interstitial sites below room temperature. This is because each is thought to be tightly bound to an oxygen atom in the host lattice to form a muonic analogue of the hydroxy group. On the basis of this concept, anomalies in SR spectra observed in oxides have been attributed in most cases to the intrinsic properties of host materials. On the other hand, global diffusion with an activation energy of 0.1~eV has been reported in some chemically-substituted perovskite oxides at cryogenic temperatures, although the reason for the small activation energy despite the formation of the strong O bond has not yet been quantitatively understood. In this study, we investigated interstitial diffusion in the perovskite oxide lattice using KTaO cubic perovskite as a model system. We used the SR method and density functional theory calculations along with the harmonic transition state theory to study this phenomenon both experimentally and theoretically. Experimental activation energies for global diffusion obtained below room temperature were less than a quarter of the calculated classical potential barrier height for a bottleneck transfer path. The reduction in the effective barrier height could be explained by the harmonic transition state theory with a zero-point energy correction; a significant difference in zero-point energies for at the positions in the O bonding equilibrium state and a bond-breaking transition state was the primary cause of the reduction. This suggests that the assumption of immobile in solid oxides is not always satisfied since such a significant decrease in diffusion barrier height can also occur in other oxides.