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論文

Magnetism induced by interlayer electrons in the quasi-two-dimensional electride Y$$_{2}$$C; Inelastic neutron scattering study

玉造 博夢; 村上 洋一*; 倉本 義夫*; 佐賀山 基*; 松浦 直人*; 川北 至信; 松石 聡*; 鷲尾 康仁*; 井下 猛*; 浜田 典昭*; et al.

Physical Review B, 102(22), p.224406_1 - 224406_5, 2020/12

Magnetic excitations in layered electride Y$$_{2}$$C have been found by inelastic neutron scattering. We have observed weak but clear magnetic scattering around the wave number $$Q = 0$$, but no magnetic order down to the lowest temperature measured (7 K). The imaginary part of the dynamical susceptibility deduced is well described by the Lorentz function of energy $$E$$ for each momentum $$Q$$. The width $$mathit{Gamma}(Q)$$ of the Lorentzian is proportional to $$Q(Q^2+kappa^{2})$$ with $$kappa^{-1} sim 4{rm AA}$$ at $$T=7$$ K. We have also found that with increasing $$Q$$ the magnetic form factor decays faster than that of a $$4d$$ electron in a single Y atom, which indicates a more extended magnetic moment in Y$$_{2}$$C. These results provide experimental evidence that the itinerant magnetism in Y$$_{2}$$C originates from the anionic electrons that reside in the interlayers. The Curie-Weiss-like behavior of the magnetic susceptibility reported in Y$$_{2}$$C is ascribed to the mode coupling effects of spin fluctuations.

論文

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

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.

論文

Suppression of decay widths in singly heavy baryons induced by the $$U_A(1)$$ anomaly

川上 洋平*; 原田 正康*; 岡 眞; 鈴木 渓

Physical Review D, 102(11), p.114004_1 - 114004_9, 2020/12

ダイクォーク描像をもとに作られたカイラル有効理論に基づいて、ヘビークォークを1個含むバリオン励起状態の崩壊幅を計算した。その結果、軸性U(1)対称性をあらわに破るアノーマリーの効果が、崩壊の結合定数を大きく減らすため、幅が10倍程度抑制されることを発見した。

論文

Nuclear magnetic relaxation time near the compensation temperature in a ferrimagnetic insulator

森 道康

Journal of the Physical Society of Japan, 89(11), p.114705_1 - 114705_7, 2020/11

 被引用回数:0

The nuclear magnetic relaxation time $$T_1$$ in a ferrimagnetic insulators is calculated within the mean-field approximation for the magnetic exchange interactions and the Raman process involving the hyperfine interaction. We find that the value of 1/$$T_1$$ on one type of site increases rapidly near the compensation temperature $$T_0$$, whereas that on the other type of site does not increase up to Curie temperature $$T_c$$. This is due to the fact that the soft-magnon bandwidth becomes comparable to $$T_0$$. An increase in 1/$$T_1$$ below $$T_c$$ is found also in another type ferrimagnet, which shows a hump structure in the temperature dependence of magnetization instead of compensation. Also in that case, we find the rapid increase in 1/$$T_1$$ below $$T_c$$, even though the magnetization does not show compensation. The coexistence of soft and hard magnons leads to these remarkable properties of ferrimagnets.

論文

Non-reciprocal pumping of surface acoustic waves by spin wave resonance

山本 慧; Yu, W.*; Yu, T.*; Puebla, J.*; Xu, M.*; 前川 禎通*; Bauer, G.*

Journal of the Physical Society of Japan, 89(11), p.113702_1 - 113702_5, 2020/11

 被引用回数:0

We predict that surface acoustic waves are generated preferentially in one direction in a heterostructure of a thin magnetic film on a non-magnetic substrate. The non-reciprocity arises from magneto-elastic coupling and magneto-rotation coupling, the former being dominant for YIG/GGG heterostructures. For YIG films thinner than about 100 nm, the surface acoustic wave amplitude is nearly unidirectional at certain angles of the in-plane equilibrium magnetisation. We compute the full magnetic field dependence of the effect for a selected device.

論文

Coexistence of two components in magnetic excitations of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ ($$x$$ = 0.10 and 0.16)

佐藤 研太朗*; 池内 和彦*; 梶本 亮一; 脇本 秀一; 新井 正敏*; 藤田 全基*

Journal of the Physical Society of Japan, 89(11), p.114703_1 - 114703_7, 2020/11

 被引用回数:0

To elucidate the spin dynamics of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$, which couples with the charge degree of freedom, the spin excitations spanning the characteristic energy ($$E_mathrm{cross}$$ $$sim$$ 35--40 meV) are investigated for underdoped $$x$$ = 0.10 and optimally doped (OP) $$x$$ = 0.16 through inelastic neutron scattering measurements. Analysis based on a two-component picture of high-quality data clarified the possible coexistence of upright standing incommensurate (IC) excitations with gapless commensurate (C) excitations in the energy-momentum space. The IC component weakens the intensity toward $$E_mathrm{cross}$$ with increasing energy transfer ($$hbaromega$$), whereas the C component strengthens at high-$$hbaromega$$ regions. The analysis results imply that the superposition of two components with a particular intensity balance forms an hourglass-shaped excitation in appearance. Furthermore, the temperature dependence of the intensity of each component exhibits different behaviors; the IC component disappears near the pseudo-gap temperature ($$T^*$$) upon warming, whereas the C component is robust against temperature. These results suggest the itinerant electron spin nature and the localized magnetism of the parent La$$_{2}$$CuO$$_{4}$$ in IC and C excitations, respectively, similar to the spin excitations in the OP YBa$$_{2}$$Cu$$_{3}$$O$$_{6+delta}$$ and HgBa$$_{2}$$CuO$$_{4+delta}$$ with higher superconducting-transition temperatures.

論文

Emergence of nearly flat bands through a kagome lattice embedded in an epitaxial two-dimensional Ge layer with a bitriangular structure

Fleurence, A.*; Lee, C.-C.*; Friedlein, R.*; 深谷 有喜; 吉本 真也*; 向井 孝三*; 山根 宏之*; 小杉 信博*; 吉信 淳*; 尾崎 泰助*; et al.

Physical Review B, 102(20), p.201102_1 - 201102_6, 2020/11

 被引用回数:0

最近、2次元の二重三角格子において、そこに内在するカゴメ格子によってフラットバンドが出現することが予測された。本研究では、ZrB$$_{2}$$薄膜上に表面偏析したGe原子がその2次元二重三角格子を形成することを報告する。角度分解光電子分光および第一原理計算から、2次元Ge二重三角格子では有意な面内の長距離ホッピングおよび基板との相互作用が存在するにも関わらず、フラットバンドが形成されることが明らかになった。このフラットバンドは、原子配置から生ずるものではなく、電子状態のカップリングに起因する。

論文

Measurement of fission-fragment mass distributions in the multinucleon transfer channels of the $$^{18}$$O+$$^{237}$$Np reaction

Vermeulen, M. J.; 西尾 勝久; 廣瀬 健太郎; Kean, K. R.; 牧井 宏之; Orlandi, R.; 塚田 和明; Tsekhanovich, I.*; Andreyev, A. N.; 石崎 翔馬*; et al.

Physical Review C, 102(5), p.054610_1 - 054610_11, 2020/11

Fission fragment mass distributions for 23 nuclei ($$^{234-237}$$U, $$^{236-239}$$Np, $$^{238-241}$$Pu, $$^{240-243}$$Am, $$^{242-245}$$Cm, and $$^{244-246}$$Bk) were measured using the multi-nucleon transfer approach in the reaction of $$^{18}$$O+$$^{237}$$Np, and their excitation-energy dependence was obtained up to a maximum of 70 MeV. Among them, the low energy fission of $$^{236}$$Np, $$^{238}$$Pu, and $$^{245}$$Cm is reported for the first time. The experimental data for all the studied nuclei were compared to the Langevin calculations. The calculation which takes into account the effects of multi-chance fission well reproduced the peak-to-valley ratio and mass-asymmetric peak positions of the distributions. The angular momenta given to the fissioning nucleus is also discussed.

論文

Competition between allowed and first-forbidden $$beta$$ decay; The Case of $$^{208}$$Hg $$rightarrow$$ $$^{208}$$Tl

Carroll, R. J.*; Podoly$'a$k, Zs.*; Berry, T.*; Grawe, H.*; Alexander, T.*; Andreyev, A. N.; Ansari, S.*; Borge, M. J. G.*; Brunet, M.*; Creswell, J. R.*; et al.

Physical Review Letters, 125(19), p.192501_1 - 192501_6, 2020/11

The $$beta$$ decay of $$^{208}$$Hg into the one-proton hole, one neutron-particle $$^{208}_{81}$$Tl$$_{127}$$ nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the $$N > 126$$, $$Z < 82$$ quadrant of neutron-rich nuclei. While both negative and positive parity states with spin 0 and 1 are expected within the $$Q_{beta}$$ window, only three negative parity states are populated directly in the $$beta$$ decay. The data provide a unique test of the competition between allowed Gamow-Teller and Fermi, and first-forbidden $$beta$$ decays, essential for the understanding of the nucleosynthesis of heavy nuclei in the rapid neutron capture process. Furthermore, the observation of the parity changing $$0^{+} rightarrow 0^{-} beta$$ decay where the daughter state is core excited is unique, and can provide information on mesonic corrections of effective operators.

論文

Anomalous magnetic anisotropy and magnetic nanostructure in pure Fe induced by high-pressure torsion straining

大場 洋次郎; 足立 望*; 戸高 義一*; Gilbert, E. P.*; 間宮 広明*

Physical Review Research (Internet), 2(3), p.033473_1 - 033473_6, 2020/11

Formation of nanosized spin misalignment was found in pure iron processed by high-pressure torsion straining. The small-angle neutron scattering profiles show that the spin misalignment remains in magnetic field up to 10 T, whereas the magnetization is almost saturated below 1 T based on the magnetic measurement. These results indicates that anomalous magnetic anisotropy is induced in pure iron via the high-pressure torsion straining.

論文

Relation between biomolecular dissociation and energy of secondary electrons generated in liquid water by fast heavy ions

土田 秀次*; 甲斐 健師; 北島 謙生*; 松谷 悠佑; 間嶋 拓也*; 斎藤 学*

European Physical Journal D, 74(10), p.212_1 - 212_7, 2020/10

 被引用回数:0

水中における生体分子と重イオンの相互作用による基礎研究は、放射線生物影響の初期段階の解明へ向けて重要な知見を与えることが期待される。その中で、生体環境を模擬した真空中の液滴標的への重イオン照射実験が進められ、液滴から真空中に飛び出した生体分子グリシンの正イオン及び負イオンの生成収量が計測されているが、その生成メカニズムは未解明であった。そこで、PHITSのイオン飛跡構造解析モードを利用し、重イオンが真空から水に侵入した界面におけるエネルギー付与量を評価し、グリシンの正イオン及び負イオン分子が生成されるメカニズムを解析した。その結果、重イオン照射により発生した2次電子が関与する電離・励起、及び解離性電子付着の誘発量は、生成されたグリシンの正イオン及び負イオンの生成収量と相関があることを見出した。本成果は、放射線生物影響の初期段階の解明へ向けて、新たな科学的知見となるものである。

論文

Photonuclear reactions in lightning, 1; Verification and modeling of reaction and propagation processes

和田 有希*; 榎戸 輝揚*; 中澤 知洋*; 小高 裕和*; 古田 禄大; 土屋 晴文

Journal of Geophysical Research; Atmospheres, 125(20), 17 Pages, 2020/10

 被引用回数:0

We report simulation results of photonuclear reactions in the atmosphere triggered by a downward terrestrial gamma-ray flash in lightning. Possible channels of reactions in the atmosphere and their cross sections are verified with the ENDF/B-VII.1 library. Monte-Carlo simulations with two stages are then performed with the Geant4 framework. In the first stage, electrons following the relativistic runaway electron avalanche spectrum are produced in a mass model of the atmosphere, and production of photoneutrons and $$beta^{+}$$-decay nuclei is calculated based on the nuclear data library. In total 1$$times$$$$10^{13}$$ neutrons and 4$$times$$$$10^{12}$$ $$beta^{+}$$-decay nuclei are produced by $$10^{18}$$ energetic electrons above 1 MeV. In the second stage, propagation of the photoneutrons and positrons from the $$beta^{+}$$-decay nuclei in the previous stage is calculated. As a result, we model on-ground distributions of fluxes and energy spectra for neutrons, neutron-related gamma rays, and annihilation ones. The simulation model is to be compared with photonuclear events detected in low-charge-center winter thunderstorms.

論文

Insight into Kondo screening in the intermediate-valence compound SmOs$$_4$$Sb$$_{12}$$ uncovered by soft X-ray magnetic circular dichroism

斎藤 祐児; 藤原 秀紀*; 保井 晃*; 門野 利治*; 菅原 仁*; 菊地 大輔*; 佐藤 英行*; 菅 滋正*; 山崎 篤志*; 関山 明*; et al.

Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10

 被引用回数:0

Through a high-precision soft X-ray magnetic circular dichroism (XMCD) study of the intermediate-valence compound SmOs$$_4$$Sb$$_{12}$$, we show our successful approach of revealing unprecedented details of Kondo screening below a characteristic temperature of $$ T_{0} sim$$ 20 K in the paramagnetic phase. The multiplet XMCD structure at the Sm $$M_{5}$$ edge sensitive to the 4$$f$$ configuration enabled us to observe a clear difference between the temperature evolution above and below $$T_{0}$$ with one- and two-component behavior, respectively. Our findings are in strong contrast to the conventional Kondo crossover that coincides with the valence transition, but are qualitatively accounted for by theoretical XMCD predictions combined with the two-fluid phenomenology recently proposed. This work contributes to the large context of Kondo physics that is closely related to quantum criticality in heavy fermion systems.

論文

Nonresonant $$p$$-wave direct capture and interference effect observed in the $$^{16}$$O$$(n,gamma)^{17}$$O reaction

永井 泰樹*; 木下 充隆*; 井頭 政之*; 延原 由利子*; 牧井 宏之; 三島 賢二*; 嶋 達志*; Mengoni, A.*

Physical Review C, 102(4), p.044616_1 - 044616_8, 2020/10

 被引用回数:0

We measured the total capture cross section of the $$^{16}$$O$$(n,gamma)^{17}$$O reaction, as well as partial cross sections leading to the ground ($$J^{pi} = 5/2^{+})$$ and first excited ($$J^{pi} = 1/2^{+})$$ states in $$^{17}$$O. The measurement was carried out at average neutron energies of 157, 349, 398, 427, 468, 498, and 556 keV by using pulsed neutrons produced via the $$^{7}$$Li$$(p,n)^{7}$$Be reaction and a $$gamma$$-ray detection system based on an anti-Compton NaI(Tl) spectrometer. We observed the interference effect between the $$3/2^{-}$$ resonance state at 4554 keV of $$^{17}$$O, corresponding to a neutron energy of 411 keV in the center-of-mass system, and a non-resonant contribution in the capture process. The measured partial cross sections are in good agreement with theoretical calculations obtained taking into account the interference between the $$3/2^{-}$$ resonance and a non-resonant p-wave direct radiative capture contribution. Using the present results, together with our previous measurement, we derived the Maxwellian-averaged capture cross sections (MACS) for thermal energies between kT = 5 and 100 keV, key quantities for ${it s}$ process nucleosynthesis studies in massive stars.

論文

$$alpha$$ decay of $$^{243}$$Fm$$_{143}$$ and $$^{245}$$Fm$$_{145}$$, and of their daughter nuclei

Khuyagbaatar, J.*; He${ss}$berger, F. P.*; Hofmann, S.*; Ackermann, D.*; Burkhard, H. G.*; Heinz, S.*; Kindler, B.*; Kojouharov, I.*; Lommel, B.*; Mann, R.*; et al.

Physical Review C, 102(4), p.044312_1 - 044312_8, 2020/10

 被引用回数:0

Nuclear structure of $$^{243}$$Fm, $$^{245}$$Fm, and their daughter nuclei were investigated via detection of their radioactive decays, $$alpha$$, $$gamma$$, and spontaneous fission. Measured $$alpha$$-decay energies, half-lives, and branching ratios improve the literature data significantly. A signature for detection of the hitherto unknown $$^{235}$$Cm was found in the $$alpha$$-decay chains from $$^{243}$$Fm. Two groups of $$alpha$$ events with average energies of 6.69(2) MeV and 7.01(2) MeV and with a half-life of $$T_{1/2}$$ = 300$$^{+250}_{-100}$$, s are suggested to originate from $$^{235}$$Cm. Tentative decay schemes for $$^{243}$$Fm, $$^{239}$$Cf, $$^{235}$$Cm, and $$^{245}$$Fm, $$^{241}$$Cf isotopes are suggested based on the present experimental data. Systematical trends of single-particle states in $$N$$=141 isotones of $$Z$$ = 92-98 nuclei are discussed.

論文

Laser-assisted decay spectroscopy and mass spectrometry of $$^{178}$$Au

Cubiss, J. G.*; Andreyev, A. N.; Barzakh, A. E.*; Manea, V.*; Al Monthery, M.*; Althubiti, N. A.*; Andel, B.*; Antalic, S.*; 他39名*

Physical Review C, 102(4), p.044332_1 - 044332_12, 2020/10

A comprehensive study of the isotope $$^{178}$$Au has been made at the CERN-ISOLDE facility, using resonance laser ionization. Two long-lived states in $$^{178}$$Au were identified - a low-spin ground state and a high-spin isomer - each of which were produced as pure beams. Using the ISOLTRAP precision Penning trap, the excitation energy of the isomeric state in $$^{178}$$Au was determined to be $$E^{*} = $$ 189(14) keV. The $$alpha$$-decay fine structure patterns of the two states were studied using the Windmill decay station, providing information on the low-lying states in the daughter nucleus $$^{174}$$Ir. Nuclear spin assignments of $$I(^{178}$$Au$$^{g}) = (2,3)$$ and $$I(^{178}$$Au$$^{m}) = (7,8)$$ are made based on the observed $$beta$$-decay feeding and hyperfine structure intensity patterns.

論文

Hexaquark picture for $$d$$*(2380)

Kim, H.*; Kim, K. S.*; 岡 眞

Physical Review D, 102(7), p.074023_1 - 074023_10, 2020/10

 被引用回数:0

$$I$$=0, $$J$$=3のダイバリオン状態の6クォーク(ヘキサクォーク)成分を分析し、質量を求めた。その結果、実験的に報告されている質量をヘキサクォーク構造から矛盾なく説明できることを示した。

論文

Optomagnonic Barnett effect

仲田 光樹; 高吉 慎太郎*

Physical Review B, 102(9), p.094417_1 - 094417_11, 2020/09

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)

いわゆる光学的Barnett効果[A. Rebei and J. Hohlfeld, Phys. Lett. A 372, 1915 (2008); J. Appl. Phys. 103, 07B118 (2008)], i.e., 円偏光レーザー誘起磁化成長[S. Takayoshi et al., Phys. Rev. B 90, 214413 (2014); S. Takayoshi et al., Phys. Rev. B 90, 085150 (2014)]をフェリ磁性絶縁体に応用し、THz領域におけるマグノン凝縮機構を微視的に解明した。これはBose統計に従うマグノンに特有の巨視的量子効果である。本研究が提供するTHzマグノン凝縮体を活用することで、従来の強磁性絶縁体中のものよりはるかに高速のスピン輸送「巨視的量子干渉効果によるJosephsonスピン流」を実現することができる。

論文

Direct measurement of fast ortho-para conversion of molecularly chemisorbed H$$_{2}$$ on Pd(210)

植田 寛和; 笹川 裕矢*; Ivanov, D.*; 大野 哲*; 小倉 正平*; 福谷 克之

Physical Review B, 102(12), p.121407_1 - 121407_5, 2020/09

 被引用回数:0 パーセンタイル:100(Materials Science, Multidisciplinary)

Pd(210)表面に化学吸着したH$$_{2}$$のオルトーパラ転換を報告する。分子線,光刺激脱離,共鳴多光子イオン化法を用いて水素の回転状態変化を調べた。実験結果から、~2秒の転換時間で転換が起こることが明らかになった。実験結果と過去の理論計算結果を比較することで、2次の摂動による転換メカニズムを支持する。

論文

Theoretical study of Nb isotope productions by muon capture reaction on $$^{100}$$Mo

Ciccarelli, M.*; 湊 太志; 内藤 智也*

Physical Review C, 102(3), p.034306_1 - 034306_9, 2020/09

 被引用回数:0 パーセンタイル:100(Physics, Nuclear)

The isotope $$^{99}$$Mo, the generator of $$^{rm 99m}$$Tc used for diagnostic imaging, is supplied by extracting from fission fragments of highly enriched uranium in reactors. However, a reactor-free production method of $$^{99}$$Mo is searched over the world from the point of view of nuclear proliferation. Recently, $${}^{99}$$Mo production through a muon capture reaction was proposed and it was found that about 50% of $$^{100}$$Mo turned into $$^{99}$$Mo through $$^{100}$$Mo$$ (mu^-,n)$$ reaction. However, the detailed physical process of the muon capture reaction is not completely understood. We, therefore, study the muon capture reaction of $$^{100}$$Mo by a theoretical approach. We used the $$pn$$ QRPA to calculate the muon capture rate. The muon wave function is calculated with considering the electronic distribution of the atom and the nuclear charge distribution. The particle evaporation process from the daughter nucleus is calculated by the Hauser-Feshbach statistical model. From the model calculation, about 38% of $$^{100}$$Mo is converted to $$^{99}$$Mo through the muon capture reaction, which is in a reasonable agreement with the experimental data. It is revealed that negative parity states, especially $$1^-$$ state, play an important role in $$^{100}$$Mo $$(mu^-,n)^{99}$$Nb. Isotope production by the muon capture reaction strongly depends on the nuclear structure. To understand the mechanism, excitation energy functions have to be known microscopically.

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