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SnHuang, 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：0TbMnSn 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.
Zhang, A.*; Deng, K.*; Sheng, J.*; Liu, P.*; Kumar, S.*; 島田 賢也*; Jiang, Z.*; Liu, Z.*; Shen, D.*; Li, J.*; et al.
Chinese Physics Letters, 40(12), p.126101_1 - 126101_8, 2023/12
被引用回数：1 パーセンタイル：0(Physics, Multidisciplinary)In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, itis predicted that in the nonrelativistic limit of certain collinear antiferromagnets, there exists a type of chiral "Dirac-like" fermion, whose dispersion manifests four-fold degenerate crossing points formed by spin-degenerate linear bands, with topologically protected Fermi arcs. Here, by combining with neutron diffraction and first-principles calculations, we suggest a multidomain collinear antiferromagnetic configuration, rendering the existence of the Fermi-arc surface states induced by chiral Dirac-like fermions.
Bao, S.*; Gu, Z.-L.*; Shangguan, Y.*; Huang, Z.*; Liao, J.*; Zhao, X.*; Zhang, B.*; Dong, Z.-Y.*; Wang, W.*; 梶本 亮一; et al.
Nature Communications (Internet), 14, p.6093_1 - 6093_9, 2023/09
被引用回数：1 パーセンタイル：61.99(Multidisciplinary Sciences)Magnon polarons are novel elementary excitations possessing hybrid magnonic and phononic signatures, and are responsible for many exotic spintronic and magnonic phenomena. Despite long-term sustained experimental efforts in chasing for magnon polarons, direct spectroscopic evidence of their existence is hardly observed. Here, we report the direct observation of magnon polarons using neutron spectroscopy on a multiferroic Fe
Mo
O
possessing strong magnon-phonon coupling. Specifically, below the magnetic ordering temperature, a gap opens at the nominal intersection of the original magnon and phonon bands, leading to two separated magnon-polaron bands. Each of the bands undergoes mixing, interconverting and reversing between its magnonic and phononic components. We attribute the formation of magnon polarons to the strong magnon-phonon coupling induced by Dzyaloshinskii-Moriya interaction. Intriguingly, we find that the band-inverted magnon polarons are topologically nontrivial. These results uncover exotic elementary excitations arising from the magnon-phonon coupling, and offer a new route to topological states by considering hybridizations between different types of fundamental excitations.
Jiang, X.*; 服部 高典; Xu, X.*; Li, M.*; Yu, C.*; Yu, D.*; Mole, R.*; 矢野 真一郎*; Chen, J.*; He, L.*; et al.
Materials Horizons, 10(3), p.977 - 982, 2023/03
被引用回数：5 パーセンタイル：87.86(Chemistry, Multidisciplinary)現在の蒸気圧縮式冷凍機に代わる環境に優しい冷凍機として、バロカロリック効果に基づく固体冷凍機が世界的に注目されている。一般に、バロカロリック効果が発現する相はいずれも常圧でも存在する。ここでは、それらの物質と違って、KPFが高圧の菱面体晶相を生成することにより、巨大なバロカロリック効果を示すことを実証した。相図は、圧力依存の熱量測定、ラマン散乱測定、中性子回折測定に基づいて構築されたものである。本研究は、巨大バロカロリー効果に、高圧相の生成という新たな手法をもたらすと期待される。
BaCo(PO
)Sheng, J.*; Wang, L.*; Candini, A.*; Jiang, W.*; Huang, L.*; Xi, B.*; Zhao, J.*; Ge, H.*; Zhao, N.*; Fu, Y.*; et al.
Proceedings of the National Academy of Sciences of the United States of America, 119(51), p.e2211193119_1 - e2211193119_9, 2022/12
被引用回数：3 パーセンタイル：28(Multidisciplinary Sciences)Although considerable progress has been made in the theoretical understanding of the low-dimensional frustrated quantum magnets, experimental realizations of a well-established scaling analysis are still scarce. This is particularly true for the two-dimensional antiferromagnetic triangular lattices. Owing to the small exchange strength, the newly discovered compound NaBaCo(PO) provides a rare opportunity for clarifying the quantum criticality in an ideal triangular lattice with quantum spin S=1/2. In addition to the establishment of the complete phase diagrams, the spin Hamiltonian with a negligible interplane interaction has been determined through the spin wave dispersion in the polarized state, which is consistent with the observation of a two-dimensional quantum critical point with the Bose-Einstein condensation of diluted free bosons.
Boznar, M. Z.*; Charnock, T. W.*; Chouhan, S. L.*; Grsic, Z.*; Halsall, C.*; Heinrich, G.*; Helebrant, J.*; Hettrich, S.*; Ku
a, P.*; Mancini, F.*; et al.
IAEA-TECDOC-2001, 226 Pages, 2022/06
IAEAは、2012年から2015年にかけて、放射線影響評価のためのモデリングとデータに関する(MODARIA)プログラムを組織した。MODARIAプログラムは、環境放射線量評価の分野において、改善されたデータの取得、モデルの試験、モデルの入力・仮定・出力の比較、モデリングの考え方に関する合意形成、アプローチとパラメータ値の調整、改善された方法の開発、情報交換を行うことで能力を高めることを目的としたものである。本書は、第2ワーキンググループ「汚染された都市環境における被ばくと修復措置の効果」の活動について述べたものである。
Thiessen, K. M.*; Boznar, M. Z.*; Charnock, T. W.*; Chouhan, S. L.*; Federspiel, L.; Gra
i, B.*; Grsic, Z.*; Helebrant, J.*; Hettrich, S.*; Hulka, J.*; et al.
Journal of Radiological Protection, 42(2), p.020502_1 - 020502_8, 2022/06
被引用回数：5 パーセンタイル：78.52(Environmental Sciences)The IAEA's model testing programmes (1988-2019) have included a series of Working Groups concerned with modelling radioactive contamination in urban environments. This paper describes the exercises conducted during the MODARIA I (2012-2015) and MODARIA II (2016-2019) programmes. These exercises have included short-range and mid-range atmospheric dispersion exercises based on data from field tests or tracer studies, hypothetical urban dispersion exercises, and an exercise based on data collected after the Fukushima accident. Improvement of model capabilities will lead to improvements in assessing various contamination scenarios (real or hypothetical), and in turn, to improved decision-making and communication with the public following a nuclear or radiological emergency.
scaling of the vibrational density of states in quasi-2D nanoconfined solidsYu, Y.*; Yang, C.*; Baggioli, M.*; Phillips, A. E.*; Zaccone, A.*; Zhang, L.*; 梶本 亮一; 中村 充孝; Yu, D.*; Hong, L.*
Nature Communications (Internet), 13, p.3649_1 - 3649_10, 2022/06
被引用回数：8 パーセンタイル：81.66(Multidisciplinary Sciences)The vibrational properties of crystalline bulk materials are well described by Debye theory, which successfully predicts the quadratic 
low-frequency scaling of the vibrational density of states. However, the analogous framework for nanoconfined materials with fewer degrees of freedom has been far less well explored. Using inelastic neutron scattering, we characterize the vibrational density of states of amorphous ice confined inside graphene oxide membranes and we observe a crossover from the Debye scaling to an anomalous behaviour upon reducing the confinement size L.
高木 里奈*; 松山 直文*; Ukleev, V.*; Yu, L.*; White, J. S.*; Francoual, S.*; Mardegan, J. R. L.*; 速水 賢*; 齋藤 開*; 金子 耕士; et al.
Nature Communications (Internet), 13, p.1472_1 - 1472_7, 2022/03
被引用回数：55 パーセンタイル：99.61(Multidisciplinary Sciences)Magnetic skyrmions are topologically stable swirling spin textures with particle-like character, and have been intensively studied as a candidate of high-density information bit. While magnetic skyrmions were originally discovered in noncentrosymmetric systems, recently a nanometric skyrmion lattice has also been reported for centrosymmetric rare-earth compounds. For the latter systems, a novel skyrmion formation mechanism mediated by itinerant electrons has been proposed, and the search of a simpler model system allowing for a better understanding of their intricate magnetic phase diagram is highly demanded. Here, we report the discovery of square and rhombic lattices of nanometric skyrmions in a centrosymmetric binary compound EuAl
, by performing small-angle neutron and resonant elastic X-ray scattering experiments. Unlike previously reported centrosymmetric skyrmion-hosting materials, EuAl shows multiple-step reorientation of the fundamental magnetic modulation vector as a function of magnetic field, probably reflecting a delicate balance of associated itinerant-electron-mediated interactions. The present results demonstrate that a variety of distinctive skyrmion orders can be derived even in a simple centrosymmetric binary compound, which highlights rare-earth intermetallic systems as a promising platform to realize/control the competition of multiple topological magnetic phases in a single material.
GeTeBao, S.*; Wang, W.*; Shangguan, Y.*; Cai, Z.*; Dong, Z.-Y.*; Huang, Z.*; Si, W.*; Ma, Z.*; 梶本 亮一; 池内 和彦*; et al.
Physical Review X, 12(1), p.011022_1 - 011022_15, 2022/02
被引用回数：11 パーセンタイル：78.27(Physics, Multidisciplinary)In the local or itinerant extreme, magnetic excitations can be described by the Heisenberg model which treats electron spins as localized moments, or by the itinerant-electron model where the exchange interaction between electrons leads to unequal numbers of electrons with up and down spins. However, the nature of the magnetic excitations has been elusive when both local moments and itinerant electrons are present in the intermediate range. Using inelastic neutron scattering, we provide direct spectroscopic evidence on the coexistence of and interplay between local moments and itinerant electrons in a van der Waals metallic ferromagnet Fe
GeTe, which can sustain tunable room-temperature ferromagnetism down to the monolayer limit. We find that there exist ferromagnetic spin-wave excitations dispersing from the zone center at low energies resulting from local moments and a columnlike broad continuum at the zone boundary at high energies up to over 100 meV resulting from itinerant electrons. Unlike the two-dimensional crystal structure, the low-energy mode exhibits a three-dimensional nature, and the high-energy mode also has an out-of-plane dependence. Both modes persist well above the Curie temperature of 160 K. Our neutron spectroscopic data reveal that the low-energy spin waves at 100 K are more coherent than those at 4 K, which is evidence of the weakening of the Kondo screening at high temperatures. These results unambiguously demonstrate the coexistence of local moments and itinerant electrons and the Kondo effect between these two components in FeGeTe. Such behaviors are generally expected in heavy-fermion systems with heavy 
electrons but are rarely clearly observed in materials with light 
electrons. These findings shed light on the understanding of magnetism in transition-metal compounds.
CuTeOShangguan, 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
被引用回数：1 パーセンタイル：7.92(Materials Science, Multidisciplinary)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 NaCuTeO 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 
-axis. The excitation gap is of 
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 NaCuTeO, but also for the universality of the strongly correlated state in a broad range of quantum magnetic systems.
小山田 耕二*; Yu, L.*; 河村 拓馬; 小西 克己*
International Journal of Modeling, Simulation, and Scientific Computing, 12(2), p.2140001_1 - 2140001_19, 2021/04
流体や気象,宇宙観測など様々な分野においてセンサー技術が向上し、そこから得られたビッグデータに対して偏微分方程式(PDE)による説明モデルを導出することは重要な課題である。本論文では、時空間的に離散した点群データを対象にして、高階の微分を含む線形のPDEを推定する技術を提案する。この技術では点群データを学習したニューラルネットワーク(NN)から時間・空間の微分値を計算し、回帰分析技術を用いてPDEの微分項を推定する。実験では、厳密解を持つPDEを対象にして、様々なメタパラメータに対して推定PDEの誤差を計算した。その結果、NNの階層を厳密解のPDEに含まれる微分項の階数に合わせて増やし、回帰分析の手法としてLASSOによるL1正則化を採用することでモデルの精度が高まると分かった。
TeOBao, S.*; Cai, Z.*; Si, W.*; Wang, W.*; Wang, X.*; Shangguan, Y.*; Ma, Z.*; Dong, Z.-Y.*; 梶本 亮一; 池内 和彦*; et al.
Physical Review B, 101(21), p.214419_1 - 214419_8, 2020/06
被引用回数：17 パーセンタイル：74.78(Materials Science, Multidisciplinary)We perform thermodynamic and inelastic neutron scattering (INS) measurements to study the lattice dynamics (phonons) of a cubic collinear antiferromagnet CuTeO which hosts topological spin excitations (magnons). While the specific heat and thermal conductivity results show that the thermal transport is dominated by phonons, the deviation of the thermal conductivity from a pure phononic model indicates that there is a strong coupling between magnons and phonons. In the INS measurements, we find a mode in the excitation spectra at 4.5 K, which exhibits a slight downward dispersion around the Brillouin zone center. This mode disappears above the N
el temperature and thus cannot be a phonon. Furthermore, the dispersion is distinct from that of a magnon. Instead, it can be explained by the magnon-polaron mode, collective excitations resulting from the hybridization between magnons and phonons. We consider the suppression of the thermal conductivity and emergence of the magnon-polaron mode to be evidence for magnon-phonon coupling in CuTeO.
Mn
SbCai, Z.*; Bao, S.*; Wang, W.*; Ma, Z.*; Dong, Z.-Y.*; Shangguan, Y.*; Wang, J.*; Ran, K.*; Li, S.*; 蒲沢 和也*; et al.
Physical Review B, 101(13), p.134408_1 - 134408_10, 2020/04
被引用回数：6 パーセンタイル：38.95(Materials Science, Multidisciplinary)ディラック物質は量子現象と共にキャリアの役割を探索するのに良い系で、磁気ワイル半金属のSrMnSbはワイルフェルミオンとマグノンの関係を研究する良い舞台である。本研究では、SrMnSbの単結晶の中性子非弾性散乱実験を行い、磁性Mn層の分散は約76meVまで広がり、層間の分散は6meVの狭いバンド幅を持つことを見出した。また、これらの実験結果はハイゼンベルグ・スピンハミルトニアンを用いた線形スピン波理論によって再現可能である。本研究では、ワイルフェルミオンとマグノンが共存しているにもかかわらず、SrMnSb中のワイルフェルミオンが磁気ダイナミクスに影響を与えているという明確な証拠は得られなかった。これは、ワイルフェルミオンとマグノンがSb層とMn層に別々に存在し、この擬二次元性による層間結合の弱さに起因するもの考えられる。
decay of 
USun, M. D.*; Liu, Z.*; Huang, T. H.*; Zhang, W. Q.*; Andreyev, A. N.; Ding, B.*; Wang, J. G.*; Liu, X. Y.*; Lu, H. Y.*; Hou, D. S.*; et al.
Physics Letters B, 800, p.135096_1 - 135096_5, 2020/01
被引用回数：11 パーセンタイル：79.42(Astronomy & Astrophysics)Fine structure in the decay of U was observed in the fusion-evaporation reaction 
Re(
Ar,p3n) by using fast digital pulse processing technique. Two -decay branches of U feeding the ground state and 244 keV excited state of 
Th were identified by establishing the decay chain U
Th
Ra
Rn. The -particle energy for the ground-state to ground-state transition of U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62
s. Evolution of nuclear structure for 
=131 even-
isotones from Po to U was discussed in the frameworks of nuclear mass and reduced -decay width, a weakening octupole deformation in the ground state of U relative to its lighter isotones Ra and Th was suggested.
Li, B.; Wang, H.*; 川北 至信; Zhang, Q.*; Feygenson, M.*; Yu, H. L.*; Wu, D.*; 尾原 幸治*; 菊地 龍弥*; 柴田 薫; et al.
Nature Materials, 17(3), p.226 - 230, 2018/03
被引用回数：121 パーセンタイル：96.83(Chemistry, Physical)As a generic property, all substances transfer heat through microscopic collisions of constituent particles. A solid conducts heat through both transverse and longitudinal acoustic phonons, but a liquid employs only longitudinal vibrations. As a result, a solid is usually thermally more conductive than a liquid. In canonical viewpoints, such a difference also serves as the dynamic signature distinguishing a solid from a liquid. Here, we report liquid-like thermal conduction observed in the crystalline AgCrSe. The transverse acoustic phonons are completely suppressed by the ultrafast dynamic disorder while the longitudinal acoustic phonons are strongly scattered but survive, and are thus responsible for the intrinsically ultralow thermal conductivity. This scenario is applicable to a wide variety of layered compounds with heavy intercalants in the van der Waals gaps, manifesting a broad implication on suppressing thermal conduction. These microscopic insights might reshape the fundamental understanding on thermal transport properties of matter and open up a general opportunity to optimize performances of thermoelectrics.
Yu, Q.*; Qi, L.*; 都留 智仁; Traylor, R.*; Rugg, D.*; Morris, J. W. Jr.*; Asta, M.*; Chrzan, D. C.*; Minor, A. M.*
Science, 347(6222), p.635 - 639, 2015/02
被引用回数：240 パーセンタイル：98.35(Multidisciplinary Sciences)溶質元素がらせん転位の長距離弾性場と弱い相互作用をすることを考慮して、固溶硬化は可動転位と比較的弱い影響しか持たないとこれまで考えられてきた。この考えは転位芯との強い相互作用を示した第一原理計算によって覆されようとしている。我々は六方晶のチタンを対象に実験と計算から顕著な強化機構について検討を行った。高解像度その場観察電子顕微鏡を駆使して、柱面を運動するらせん転位と酸素が非常に強い相互作用をすることを示した。また、第一原理計算から、格子間型の溶質酸素が転位芯と短距離ながら強い結合を生じることを明らかにした。これらは酸素原子近傍の転位のピン留め機構を生じ、従来の知見と異なり格子間固溶元素が強化機構に重要な役割を持つことを示している。
佐甲 博之; Ahn, J. K.*; Baek, K. H.*; Bassalleck, B.*; Fujioka, H.*; Guo, L.*; 長谷川 勝一; Hicks, K.*; Honda, R.*; Hwang, S. H.*; et al.
Journal of Instrumentation (Internet), 9(4), p.C04009_1 - C04009_10, 2014/04
被引用回数：3 パーセンタイル：16.04(Instruments & Instrumentation)(
,
)反応によるHダイバリオン探索実験(J-PARC E42)のためのTPCの開発を行っている。TPCにおいてHが2個の
と2個の
に崩壊する事象を測定する。TPCのドリフト体積は50cm直径、55cmドリフト長を持つ8角柱構造をしておりAr-CHガスを使用する。増幅部には3層のGEMを使用する。荷電粒子の運動量測定のためTPCにはドリフト電場と平行に鉛直方向の1Tの双極磁場を超伝導ヘルムホルツ型磁石によりかける。H崩壊のアクセプタンスを最大にするためダイアモンド標的がTPC内部の筒状の穴に設置される。さらに、超高レートのビームをTPCに直接照射するため陽イオンフィードバックを極力抑制必要がある。このためTPCにGEMとgating gridを採用した。
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：73 パーセンタイル：91.83(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
for Zn, respectively. Isostructural to (Ga,Mn)As, Li(Zn,Mn)P was found to be a 
-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.
implantation and subsequent thermal annealingYu, R. S.*; 前川 雅樹; 河裾 厚男; Wang, B. Y.*; Wei, L.*
Nuclear Instruments and Methods in Physics Research B, 270, p.47 - 49, 2012/01
被引用回数：7 パーセンタイル：43.52(Instruments & Instrumentation)Positron annihilation in 800 keV Ge implanted hexagonal SiC was studied by thermal annealing at temperatures ranging from 800 to 1400 
C. The variation in Doppler broadening 
values as a function of the incident positron energy suggests a broad distribution in the depth of vacancy defects in the implanted samples. Increasing the annealing temperature triggers the accumulation of vacancies into vacancy clusters. After annealing at 1400 C, defects in the deep region of SiC are eliminated, and Ge precipitation is believed to appear in the sample at the same time. Though Ge has a much more negative positron affinity than SiC, positron annihilation coincidence Doppler broadening measurement reveals that a preferential trapping of positrons in Ge seems impossible.
