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Direct observation of topological magnon polarons in a multiferroic material

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

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$$_{2}$$Mo$$_{3}$$O$$_{8}$$ 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.


Single crystal growths and magnetic properties of hexagonal polar semimetals $$R$$AuGe ($$R$$ = Y, Gd-Tm, and Lu)

車地 崇*; 厳 正輝*; 鬼頭 俊介*; 池内 和彦*; 中村 充孝; 池田 暁彦*; 有馬 孝尚*

Journal of Alloys and Compounds, 947, p.169475_1 - 169475_8, 2023/06

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

We study structural and magnetic properties of rare-earth based semimetals ${it R}$AuGe (${it R}$ = Y, Gd-Tm, and Lu) using flux-grown single crystals. We evaluate the crystal electric field parameters based on the Stevens operators to reasonably reproduce the temperature dependence of magnetic susceptibilities and specific heat for RAuGe (${it R}$ = TbTm). The estimated energy scale of the Ising gap ($$sim$$ 11 meV) in TmAuGe is consistent with an excitation observed in an inelastic neutron scattering experiment. These findings suggest an opportunity for interplay between conduction electrons and nontrivial spin structures in the family of magnetic polar semimetals ${it R}$AuGe.


Experimental evidence for the significance of optical phonons in thermal transport of tin monosulfide

Wu, P.*; 村井 直樹; Li, T.*; 梶本 亮一; 中村 充孝; 古府 麻衣子; 中島 健次; Xia, K.*; Peng, K.*; Zhang, Y.*; et al.

New Journal of Physics (Internet), 25(1), p.013032_1 - 013032_11, 2023/01

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

The understanding of the lattice dynamics is essential for engineering the thermal transport properties in quantum materials. Based on the canonical point of view, acoustic phonons are believed to be the principal thermal carriers in heat flow. Here, in this work, optical phonons are elucidated to play a pivotal role in determining the lattice thermal conductivity in thermoelectric material SnS by using the state-of-the-art inelastic neutron scattering technique combined with first-principles calculations. Additionally, in contrast to acoustic phonons, optical phonons are observed to exhibit pronounced softening and broadening with temperature. Our observations not only shed light on the significance of the optical phonons in thermal transport but also provide a vital clue to suppress the propagation of optical phonons to optimize the thermoelectric performance of SnS.


Magnon mode transition in real space

飯田 一樹*; 樹神 克明; 稲村 泰弘; 中村 充孝; Chang, L.-J.*; 社本 真一

Scientific Reports (Internet), 12, p.20663_1 - 20663_7, 2022/12

 被引用回数:0 パーセンタイル:0(Multidisciplinary Sciences)



Possible future upgrades of the direct-geometry chopper spectrometer 4SEASONS

梶本 亮一; 中村 充孝; 蒲沢 和也*; 稲村 泰弘; 飯田 一樹*; 池内 和彦*; 石角 元志*

EPJ Web of Conferences, 272, p.02007_1 - 02007_8, 2022/11

4SEASONS is a direct geometry time-of-flight spectrometer installed in the Materials and Life Science Experimental Facility, the Japan Proton Accelerator Research Complex. It is used to study atomic andspin dynamics in the energy range of $$10^0$$ meV to $$10^2$$ meV. Since more than a decade has crossed after the first inelastic scattering experiment, it is essential to consider upgrading the instrument to improve its flexibility and performance. In this paper, we discuss the possible medium-term upgrades of key components of the instrument like the chopper system, which are achievable with the current technology and at reasonable cost. Herein, we demonstrated that 4SEASONS can improve the energy resolution by a factor of two, remove frame overlap of adjacent incident energies, significantly improve the asymmetry in the pulse shape, and increase the flux by a factor of $$sim$$1.5, without major technical difficulties.


Hydrogen vibration excitations of ZrH$$_{1.8}$$ and TiH$$_{1.84}$$ up to 21 GPa by incoherent inelastic neutron scattering

服部 高典; 中村 充孝; 飯田 一樹*; 町田 晃彦*; 佐野 亜沙美; 町田 真一*; 有馬 寛*; 大下 英敏*; 本田 孝志*; 池田 一貴*; et al.

Physical Review B, 106(13), p.134309_1 - 134309_9, 2022/10

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

量子調和振動子(QHO)で近似できる蛍石型のZrH$$_{1.8}$$とTiH$$_{1.84}$$の水素の振動励起を非弾性非干渉性中性子散乱によって21GPaおよび4GPaまで調べた。第一励起の振動エネルギー$$E_1$$はそれぞれ$$E_1$$(meV) = 141.4(2) + 1.02(2)$$P$$(GPa)および$$E_1$$(meV) = 149.4(1) + 1.21(8)$$P$$(GPa)で表され、圧力とともに上昇した。格子定数の圧力変化と組み合わせて得られた金属水素原子間距離($$d_{M-H}$$)と$$E_1$$の関係は、$$E_1$$(meV) = 1.62(9)$$times$$ 10$$^3$$ $$d_{M-H}^{-3.31(8)}$$($AA)$および$$E_1$$(meV) = 1.47(21)$$times$$ 10$$^3$$ $$d_{M-H}^{-3.5(2)}$$($AA)$であった。これらのカーブの傾きは、様々な蛍石型の金属水素化物の常圧下のトレンドに比べ、急峻であった。$$E_1$$から得られた水素波動関数の広がりは、格子間サイトよりも縮み易いことが分かった。高圧下における水素の波動関数の優先的な収縮や小さな$$d_{M-H}$$における$$E_1$$の急峻な立ち上がりは金属原子のイオンコアが水素原子よりも堅いために水素原子が高圧下でより狭い領域に閉じ込められるために起こると考えられる。


The $$omega^{3}$$ scaling of the vibrational density of states in quasi-2D nanoconfined solids

Yu, 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

The vibrational properties of crystalline bulk materials are well described by Debye theory, which successfully predicts the quadratic $$omega^{2}$$ 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 $$omega^{2}$$ scaling to an anomalous $$omega^{3}$$ behaviour upon reducing the confinement size L.



勅使河原 誠; 中村 充孝; 金正 倫計; 曽山 和彦

JAEA-Technology 2021-022, 208 Pages, 2022/02


J-PARCの定格出力1MWの物質・生命科学実験施設において、今後の具体的かつ現実的な高度化戦略を展開するため、線源性能に大きく影響する加速器技術(リニアックおよびRCS)、線源技術、中性子・ミュオン輸送技術、検出技術、そしてそれらが結実する中性子・ミュオン ビーム利用装置等の現状(所期設計値に対する到達度)について整理した。さらに、現状分析に基づき出力増強に向けた改良点等について報告する。


Observation of adsorbed hydrogen species on supported metal catalysts by inelastic neutron scattering

吉田 寿雄*; 山本 旭*; 細川 三郎*; 山添 誠司*; 吉川 聡一*; 原 賢二*; 中村 充孝; 蒲沢 和也*; 田中 庸裕*

Topics in Catalysis, 64(9-12), p.660 - 671, 2021/08

 被引用回数:2 パーセンタイル:12.7(Chemistry, Applied)

Inelastic neutron scattering (INS) enables direct and selective observation of H species due to the extremely large incoherent neutron scattering cross section of a hydrogen atom. In the present study, the adsorbed H species on some heterogeneous precious metal catalysts supported by alumina and carbon black were investigated by in situ INS spectroscopy with a newly designed sample cell. Three alumina-supported metal catalysts having Pt, Pd, and Rh metal nanoparticles with different particle sizes exhibited different INS spectra in intensities and band distribution. Observation of the H species on the metal nanoparticles and the alumina surface revealed their properties. In addition, the H atoms stored in Pd nanoparticles were observed as palladium hydride. In contrast, the H species on a Pt catalyst supported by carbon black were found to be strongly adsorbed on the carbon support.


Detection of hydroxyl and hydride functional groups in a ceria crystal under hydrogen reduction

松川 健*; 飯田 一樹*; 中村 充孝; 石垣 徹*

CrystEngComm (Internet), 23(12), p.2355 - 2359, 2021/03

 被引用回数:3 パーセンタイル:59.03(Chemistry, Multidisciplinary)

Neutron powder diffraction analysis revealed that ceria transformed into the oxyhydroxide structure by hydrogen treatment. Due to detection of the vibrational modes of both OH and CeH functional groups by inelastic neutron scattering measurements, the CeH functional group was revealed to possibly exist in ceria as an aperiodic structure.


Mode distribution analysis for superionic melt of CuI by coherent quasielastic neutron scattering

川北 至信; 菊地 龍弥*; 田原 周太*; 中村 充孝; 稲村 泰弘; 丸山 健二*; 山内 康弘*; 河村 聖子; 中島 健次

JPS Conference Proceedings (Internet), 33, p.011071_1 - 011071_6, 2021/03




Magnetic excitations of Sr$$_{3}$$Ir$$_{2}$$O$$_{7}$$ observed by inelastic neutron scattering technique

藤田 全基*; 池内 和彦*; 梶本 亮一; 中村 充孝

Journal of the Physical Society of Japan, 90(2), p.025001_1 - 025001_2, 2021/02

 被引用回数:1 パーセンタイル:17.91(Physics, Multidisciplinary)

In this short note, we report on the first inelastic neutron scattering (INS) study on high-energy magnetic excitations in Sr$$_{3}$$Ir$$_{2}$$O$$_{7}$$. We observed excitations between $$sim$$80 meV and $$sim$$180 meV. The peak position of the excitations is consistent with the dispersion of a single magnon determined by resonant inelastic X-ray scattering (RIXS) measurement. Thus, our results demonstrate the feasibility of INS for iridates, which has a large neutron absorption cross-section.


Identification of hydrogen species on Pt/Al$$_{2}$$O$$_{3}$$ by ${it in situ}$ inelastic neutron scattering and their reactivity with ethylene

山添 誠司*; 山本 旭*; 細川 三郎*; 福田 良一*; 原 賢二*; 中村 充孝; 蒲沢 和也*; 佃 達哉*; 吉田 寿雄*; 田中 庸裕*

Catalysis Science & Technology, 11(1), p.116 - 123, 2021/01

 被引用回数:5 パーセンタイル:31.32(Chemistry, Physical)

Hydrogen (H) species adsorbed on catalyst surfaces are key intermediates in catalytic hydrogenation reactions over supported metal catalysts. However, individual identification of H species on the metal catalysts has not been established to date. Here, we elucidated the H species on Pt/Al$$_{2}$$O$$_{3}$$ by the combination of ${it in situ}$ inelastic neutron scattering (INS) and density functional theory (DFT). Several H species in the presence of H$$_{2}$$ were successfully identified at different sites on the Pt surface and Al$$_{2}$$O$$_{3}$$ support. The ${it in situ}$ INS and FT-IR measurements revealed that the hydride/atop Pt-H, bridged perimeter/terrace Pt-H-Pt, and threefold Pt$$_{3}$$-H are active intermediates in the C$$_{2}$$H$$_{4}$$ hydrogenation reaction, whereas the edge Pt-H-Pt is a rather inert species. In addition, the ${it in situ}$ measurements indicate that the Al$$_{2}$$O$$_{3}$$ itself acts as hydrogen storage material by mediating AlO-H and Al-H-Al species, which serve H species in the C$$_{2}$$H$$_{4}$$ hydrogenation reaction.


Temporally decoherent and spatially coherent vibrations in metal halide perovskites

Zhang, D.*; Hu, X.*; Chen, T.*; Abernathy, D. L.*; 梶本 亮一; 中村 充孝; 古府 麻衣子; Foley, B. J.*; Yoon, M.*; Choi, J. J.*; et al.

Physical Review B, 102(22), p.224310_1 - 224310_10, 2020/12

 被引用回数:4 パーセンタイル:27.96(Materials Science, Multidisciplinary)

The long carrier lifetime and defect tolerance in metal halide perovskites (MHPs) are major contributors to the superb performance of MHP optoelectronic devices. Large polarons were reported to be responsible for the long carrier lifetime. Yet microscopic mechanisms of the large polaron formation, including the so-called phonon melting, are still under debate. Here, time-of-flight inelastic neutron scattering experiments and first-principles density-functional theory calculations were employed to investigate the lattice vibrations (or phonon dynamics) in methylammonium lead iodide, a prototypical example of MHPs. Our findings are that optical phonons lose temporal coherence gradually with increasing temperature which vanishes at the orthorhombic-to-tetragonal structural phase transition. Surprisingly, however, we found that the spatial coherence is still retained throughout the decoherence process. We argue that the temporally decoherent and spatially coherent vibrations contribute to the formation of large polarons in this metal halide perovskite.


Energy resolution and neutron flux of the 4SEASONS spectrometer revisited

梶本 亮一; 中村 充孝; 飯田 一樹*; 蒲沢 和也*; 池内 和彦*; 稲村 泰弘; 石角 元志*

Journal of Neutron Research, 22(2-3), p.99 - 107, 2020/10

The elastic energy resolution, integrated intensity, and peak intensity of the direct-geometry neutron chopper spectrometer 4SEASONS at Japan Proton Accelerator Research Complex (J-PARC) were re-investigated. This was done with respect to the incident energy and the rotation speed of the Fermi chopper using incoherent scattering of vanadium and simple analytical formulas. The model calculations reproduced the observed values satisfactorily. The present work should be useful for estimating in instrument performance in experiments.


Spin dynamics of a magnetic Weyl semimetal Sr$$_{1-x}$$Mn$$_{1-y}$$Sb$$_{2}$$

Cai, 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:40.68(Materials Science, Multidisciplinary)



Emergent spin-1 Haldane gap and ferroelectricity in a frustrated spin-$$frac{1}{2}$$ ladder

上田 宏*; 小野田 繁樹*; 山口 泰弘*; 木村 剛*; 吉澤 大智*; 森岡 俊晶*; 萩原 政幸*; 萩原 雅人*; 左右田 稔*; 益田 隆嗣*; et al.

Physical Review B, 101(14), p.140408_1 - 140408_6, 2020/04

 被引用回数:3 パーセンタイル:27.96(Materials Science, Multidisciplinary)

We report experimental and theoretical evidence that Rb$$_2$$Cu$$_2$$Mo$$_3$$O$$_{12}$$ has a nonmagnetic tetramer ground state of a two-leg ladder comprising antiferromagnetically coupled frustrated spin-$$frac{1}{2}$$ chains and exhibits a Haldane spin gap of emergent spin-1 pairs. Three spin excitations split from the spin-1 triplet by a Dzyaloshinskii-Moriya interaction are identified in inelastic neutron-scattering and electron spin resonance spectra. A tiny magnetic field generates ferroelectricity without closing the spin gap, indicating a unique class of ferroelectricity induced by a vector spin chirality order.


The $$f$$-electron state of the heavy fermion superconductor NpPd$$_5$$Al$$_2$$ and the isostructural family

目時 直人; Aczel, A. A.*; 青木 大*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; 萩原 雅人*; Hong, T.*; 芳賀 芳範; 池内 和彦*; et al.

JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03



Q dependence of magnetic resonance mode on FeTe$$_{0.5}$$Se$$_{0.5}$$ studied by inelastic neutron scattering

石角 元志*; 樹神 克明; 梶本 亮一; 中村 充孝; 稲村 泰弘; 池内 和彦*; Ji, S.*; 新井 正敏*; 社本 真一

Condensed Matter (Internet), 4(3), p.69_1 - 69_10, 2019/09



Applicability and limitations of $$G(r,E)$$ analysis transformed from the inelastic neutron scattering data

中村 充孝; 菊地 龍弥*; 川北 至信

Physica B; Condensed Matter, 567, p.61 - 64, 2019/08


 被引用回数:1 パーセンタイル:4.96(Physics, Condensed Matter)

最近、非弾性中性子散乱実験(INS)データから変換した実空間動的構造因子$$G(r,E)$$を用いた多結晶NaIのフォノンダイナミクスに関する研究報告を行った。この研究は、通常のINS実験条件(Q$$_{max} sim$$ 5$AA$^{-1}$$)であっても、物理的に十分意味のある実空間ダイナミクス情報が得られることを示したものであり、これまでに蓄積されてきた大量のINSデータの再利用と新たな視点での研究推進を促すものである。今回の発表では、$$G(r,E)$$解析の適用可能性とその限界について詳しく議論する。

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