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論文

Microscopic origin of the spin-reorientation transition in the kagome topological magnet TbMn$$_{6}$$Sn$$_{6}$$

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

TbMn$$_{6}$$Sn$$_{6}$$ 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 TbMn$$_{6}$$Sn$$_{6}$$ 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 $$4f$$ 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 TbMn$$_{6}$$Sn$$_{6}$$, despite its relatively simple ground state magnetic structure, and provide insights into the mechanisms for tuning magnetic topological materials.

論文

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.

論文

DC transport in a dissipative superconducting quantum point contact

Visuri, A.-M.*; Mohan, J.*; 内野 瞬; Huang, M.-Z.*; Esslinger, T.*; Giamarchi, T.*

Physical Review Research (Internet), 5(3), p.033095_1 - 033095_11, 2023/08

粒子ロスのある量子ポイントコンタクト系のカレント・バイアス特性を研究する。Keldysh形式を採用し、チャンネルの透過率を変化させた場合のカレントを計算した。透過率の低い場合は、散逸により低バイアス領域でのカレントの増大、散逸に対する非単調性、輸送特性における新しい構造の出現が見られる。粒子ロスによる散逸の効果は、熱浴内の有限温度効果や非弾性散乱効果とは定性的に異なることがわかった。

論文

Pressure engineering of van der Waals compound RhI$$_3$$; Bandgap narrowing, metallization, and remarkable enhancement of photoelectric activity

Fang, Y.*; Kong, L.*; Wang, R.*; Zhang, Z.*; Li, Z.*; Wu, Y.*; Bu, K.*; Liu, X.*; Yan, S.*; 服部 高典; et al.

Materials Today Physics (Internet), 34, p.101083_1 - 101083_7, 2023/05

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

層状ファンデルワールスハライドは、外部圧力に対して特に敏感であるため、目的とする性質を持つ構造にチューンすることが可能となる。一方で、圧力に非常に敏感であるという特性は、同時に目的とする機能の実現に有害な相転移や格子歪みを引き起こす可能性があるためその操作は依然として困難である。この研究では、層状RhI$$_3$$結晶が持つ極めて弱い層間結合と高い機能可変性を観察した。5GPaという適度な圧力をかけると圧力誘起相転移が起こり、積層構造に変化が現れた。驚くべきことに、この相転移は、圧力に対してほぼ直線的なバンドギャップ減少という傾向に影響を与えなかった。また、より高い圧力では、1.3eVの赤方偏移というかなり大きな調整幅を伴う金属相が観測された。さらに、RhI$$_3$$のキャリア濃度は30GPaで4桁増加し、光電流は7.8GPaで5桁増加することが確認された。これらの結果は、ファンデルワールスハライドの層状構造という特異な特徴を生かした探索、調整、理解のための新たな機会を創出し、原子レベルの薄さを持つマテリアルバイデザインに基づく将来のデバイスとして有望である。

論文

Superfluid signatures in a dissipative quantum point contact

Huang, M.-Z.*; Mohan, J.*; Visuri, A.-M.*; Fabritius, P.*; Talebi, M.*; Wili, S.*; 内野 瞬; Giamarchi, T.*; Esslinger, T.*

Physical Review Letters, 130(20), p.200404_1 - 200404_8, 2023/05

 被引用回数:1 パーセンタイル:83.24(Physics, Multidisciplinary)

スピン依存の局所的な粒子損失を伴う量子ポイントコンタクトを通して、強く相互作用する2成分フェルミ超流動輸送を測定した。高次の多重アンドレーフ反射によって実現される特徴的な非オーミック型超流動輸送は、散逸強度が超流動ギャップを超えると過剰オーミック電流に遷移することを観測した。我々は、散逸のあるサイトへのトンネル過程のある2端子の平均場モデルを開発した。Keldysh形式による計算では、観測された非平衡粒子電流を再現したが、観測された損失率やスピン流を完全に説明することはできなかった。

論文

First observation of the decay of the 13/2$$^+$$ isomer in $$^{183}$$Hg and $$B$$(${it M}$2) systematics of neutron transitions across the nuclear chart

Huang, H.*; Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Li, Z. H.*; Guo, C. Y.*; Barzakh, A. E.*; Van Duppen, P.*; Andel, B.*; et al.

Physics Letters B, 833, p.137345_1 - 137345_8, 2022/10

 被引用回数:0 パーセンタイル:0.02(Astronomy & Astrophysics)

The decay of the 13/2$$^+$$ isomeric state in $$^{183}$$Hg was observed for the first time following the $$alpha$$ decay of the 13/2$$^+$$ isomer in $$^{187}$$Pb produced in the $$^{142}$$Nd$$(^{50}$$Cr$$, 2p3n)$$ reaction. Using $$alpha$$-$$gamma$$ delayed coincidence measurements, the half-life of this isomer was measured to be 290(30) $$mu$$s. This isomer is proposed to deexcite by an unobserved low-energy $$M$$2 transition to the known 9/2$$^-$$ member of a strongly prolate-deformed 7/2$$^-$$[514] band, followed by a 105-keV $$M$$1 transition to the bandhead. A lower limit of B($$M$$2)$$geq$$0.018 W.u. was deduced for the unobserved transition. The presumed retardation is proposed to be due to the notable shape change between the initial, nearly spherical, and the final, strongly deformed, states. A similar scenario is also considered for the 13/2$$^+$$ isomer in $$^{181}$$Hg, suggesting both are cases of shape isomers. The B($$M$$2) systematics of neutron transitions across the nuclear chart is discussed.

論文

Grain orientation dependence of deformation microstructure evolution and mechanical properties in face-centered cubic high/medium entropy alloys

吉田 周平*; Fu, R.*; Gong, W.; 池内 琢人*; Bai, Y.*; Feng, Z.*; Wu, G.*; 柴田 曉伸*; Hansen, N.*; Huang, X.*; et al.

IOP Conference Series; Materials Science and Engineering, 1249, p.012027_1 - 012027_6, 2022/08

 被引用回数:0 パーセンタイル:0.83

This study revealed characteristics of the deformation behavior in high/medium entropy alloys (HEAs/MEAs) with face-centered cubic (FCC) structure. A Co$$_{60}$$Ni$$_{40}$$ alloy and a Co$$_{20}$$Cr$$_{40}$$Ni$$_{40}$$ MEA having low and high friction stresses (fundamental resistance to dislocation glide in solid solutions), respectively, but similar in other properties, including their stacking fault energy and grain sizes, were compared. The MEA exhibited a higher yield strength and work-hardening ability than those in the Co$$_{60}$$Ni$$_{40}$$ alloy at room temperature. Deformation microstructures of the Co$$_{60}$$Ni$$_{40}$$ alloy were composed of coarse dislocation cells (DCs) in most grains, and a few deformation twins (DTs) formed in grains with tensile axis (TA) nearly parallel to $$<$$111$$>$$. In the MEA, three microstructure types were found depending on the grain orientations: (1) fine DCs developed in TA$$sim$$//$$<$$100$$>$$-oriented grains; (2) planar dislocation structures (PDSs) formed in grains with other orientations; and (3) dense DTs adding to the PDSs developed in TA$$sim$$//$$<$$111$$>$$-oriented grains. The results imply difficulty in cross-slip of screw dislocations and dynamic recovery in the MEA, leading to an increase in the dislocation density and work-hardening rate. Our results suggest that FCC high-alloy systems with high friction stress inherently develop characteristic deformation microstructures advantageous for achieving high strength and large ductility.

論文

Identification of excited states in $$^{188}$$Bi and $$^{188}$$Po

Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Huang, H.*; 他37名*

Physical Review C, 106(2), p.024317_1 - 024317_11, 2022/08

 被引用回数:1 パーセンタイル:34.54(Physics, Nuclear)

The neutron-deficient $$^{188}$$Bi and $$^{188}$$Po isotopes have been studied by $$gamma$$-ray spectroscopy using the recoil-decay tagging technique with the Argonne Gas-Filled Analyzer. A new 0.25(5)-micro second isomeric state and a prompt cascade formed by 319-, 366-, and 462-keV $$gamma$$ rays have been established on top of the (10$$^{-}$$) $$alpha$$-decaying isomer in $$^{188}$$Bi. The first excited (2$$^{+}$$) state in $$^{188}$$Po was identified, its excitation energy of 242(2) keV continues the nearly constant trend for the first 2$$^{+}$$ states in $$^{190,192,194}$$Po. The state is most likely a member of a prolate rotational band built on the ground state, albeit mixing with other coexisting configurations cannot be excluded. The new results obtained in the present work provide new information to shape coexistence in bismuth and polonium isotopes near the neutron midshell at $$N$$ = 104. In this mass region, a reduction in the prompt $$gamma$$-ray yield obtained with recoil decay tagging was observed for a few nuclides, and the possible reasons are presented.

論文

Fine structure in the $$alpha$$ decay of the 8$$^{+}$$ isomer in $$^{216,218}$$U

Zhang, M. M.*; Tian, Y. L.*; Wang, Y. S.*; Zhang, Z. Y.*; Gan, Z. G.*; Yang, H. B.*; Huang, M. H.*; Ma, L.*; Yang, C. L.*; Wang, J. G.*; et al.

Physical Review C, 106(2), p.024305_1 - 024305_6, 2022/08

 被引用回数:1 パーセンタイル:34.54(Physics, Nuclear)

The extremely neutron-deficient even-even uranium isotopes $$^{216,218}$$U were produced in the complete-fusion reactions induced by impinging $$^{40}$$Ar and $$^{40}$$Ca ions on $$^{180,182,184}$$W targets. Fusion evaporation residues were separated in flight by the gas-filled recoil separator SHANS (Spectrometer for Heavy Atoms and Nuclear Structure) and subsequently identified using the recoil-$$alpha$$-correlation method. In this paper, we report on new $$alpha$$-decay activities with $$E_{alpha} = 10163(27)$$ keV for $$^{216}$$U and $$E_{alpha} = 10073(16)$$ keV for $$^{218}$$U, which decay from the 8$$^{+}$$ isomeric states of $$^{216,218}$$U into the 2$$^{+}$$ states of their daughter nuclei $$^{212,214}$$Th, respectively. The new results extend the systematics of the $$alpha$$-decay fine structure for the $$N$$ = 124 and 126 even-even isotones.

論文

Magnetic properties and electronic configurations of Mn ions in the diluted magnetic semiconductor Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ studied by X-ray magnetic circular dichroism and resonant inelastic X-ray scattering

鈴木 博人*; Zhao, G.*; 岡本 淳*; 坂本 祥哉*; Chen, Z.-Y.*; 野中 洋亮*; 芝田 悟朗; Zhao, K.*; Chen, B.*; Wu, W.-B.*; et al.

Journal of the Physical Society of Japan, 91(6), p.064710_1 - 064710_5, 2022/06

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

The magnetic properties and the electronic excitations of the new diluted magnetic semiconductor Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ have been studied by X-ray magnetic circular dichroism (XMCD) and resonant inelastic X-ray scattering (RIXS). The sum rule analysis of the XMCD spectra indicates that the Mn atoms are in the high-spin configurations of $$d^5$$, whereas the presence of competing ferromagnetic and antiferromagnetic interactions between the Mn ions reduces the net spin moment. Based on a comparison of the RIXS line shapes with those of Ga$$_{1-x}$$Mn$$_x$$As, it is concluded that the ground state of Mn in Ba$$_{1-x}$$K$$_x$$(Zn$$_{1-y}$$Mn$$_y$$)$$_2$$As$$_2$$ consists of both the $$3d^5 underline{L}$$ and $$3d^5$$ electron configurations.

論文

First observation of a shape isomer and a low-lying strongly-coupled prolate band in neutron-deficient semi-magic $$^{187}$$Pb

Zhang, W. Q.*; Andreyev, A. N.; Liu, Z.*; Seweryniak, D.*; Huang, H.*; Li, Z. H.*; Li, J. G.*; Guo, C. Y.*; 他34名*

Physics Letters B, 829, p.137129_1 - 137129_7, 2022/06

 被引用回数:3 パーセンタイル:78.01(Astronomy & Astrophysics)

Prompt and delayed $$gamma$$-ray spectroscopy of the neutron-deficient, semi-magic isotope $$^{187}$$Pb has been performed at the Argonne Gas-Filled Analyzer. A new 5.15(15)-$$mu$$s isomeric state at only 308 keV above the spherical 3/2$$^{-}$$ ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2$$^{-}$$[514] Nilsson state in the isotone $$^{185}$$Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in $$^{187}$$Pb is proposed to originate from the same configuration. The retarded character of the 308-keV transition can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The combined results of the present work and the previous $$alpha$$-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of $$^{187}$$Pb, which is well reproduced by the potential-energy surface calculations.

論文

Neutron spectroscopy evidence on the dual nature of magnetic excitations in a van der Waals metallic ferromagnet Fe$$_{2.75}$$GeTe$$_{2}$$

Bao, 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:5 パーセンタイル:79.93(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$$_{2.72}$$GeTe$$_{2}$$, 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 Fe$$_{2.72}$$GeTe$$_{2}$$. Such behaviors are generally expected in heavy-fermion systems with heavy $$f$$ electrons but are rarely clearly observed in materials with light $$d$$ electrons. These findings shed light on the understanding of magnetism in transition-metal compounds.

論文

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

 被引用回数:1 パーセンタイル:8.34(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 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.

論文

Chemical-pressure-induced point defects enable low thermal conductivity for Mg$$_{2}$$Sn and Mg$$_{2}$$Si single crystals

齋藤 亘*; 林 慶*; Huang, Z.*; 杉本 和哉*; 大山 研司*; 八方 直久*; 原田 正英; 及川 健一; 稲村 泰弘; 林 好一*; et al.

ACS Applied Energy Materials (Internet), 4(5), p.5123 - 5131, 2021/05

 被引用回数:10 パーセンタイル:66.28(Chemistry, Physical)

The development of thermoelectric (TE) materials, which can directly convert waste heat into electricity, is vital to reduce the use of fossil fuels. Mg$$_{2}$$Sn and Mg$$_{2}$$Si are promising TE materials because of their superior TE performance. In this study, for future improvement of the TE performance, point defect engineering was applied to the Mg$$_{2}$$Sn and Mg$$_{2}$$Si single crystals (SCs) via boron (B) doping. Their crystal structures were analyzed via white neutron holography and SC X-ray diffraction. Moreover, nanostructures and TE properties of the B-doped Mg$$_{2}$$Sn and Mg$$_{2}$$Si SCs were investigated. The B-doping increased the chemical pressure on the Mg$$_{2}$$Sn and Mg$$_{2}$$Si SCs, leading to induce vacancy defects as a point defect. No apparent change was observed in electronic transport, but thermal transport was significantly prevented. This study demonstrates that the vacancy defects can be controlled by the chemical pressure, and can aid in achieving a high TE performance for the Mg$$_{2}$$Sn and Mg$$_{2}$$Si SCs.

論文

Origin of magnetovolume effect in a cobaltite

Miao, P.*; Tan, Z.*; Lee, S. H.*; 石川 喜久*; 鳥居 周輝*; 米村 雅雄*; 幸田 章宏*; 小松 一生*; 町田 真一*; 佐野 亜沙美; et al.

Physical Review B, 103(9), p.094302_1 - 094302_18, 2021/03

 被引用回数:1 パーセンタイル:18.63(Materials Science, Multidisciplinary)

層状ペロブスカイトPrBaCo$$_{2}$$O$$_{5.5}$$は、熱膨張のない複合材料を作るために必要な負の熱膨張(NTE)を示す。NTEは、自発的な磁気秩序と密接に関連していることがわかっていた(磁気体積効果: MVE)。今回、われわれは、PrBaCo$$_{2}$$O$$_{5.5}$$の連続的な磁気体積効果が、本質的には不連続であり、大きな体積を持つ反強磁性絶縁体(AFILV)から、小さな体積をもつ強磁性卑絶縁体(FLISV)への磁気電気的相転移に起因することを明らかにした。また、磁気電気効果(ME)は、温度,キャリアドーピング,静水圧,磁場などの複数の外部刺激に対して高い感度を示した。これは、これまでよく知られている対称性の破れを伴う巨大磁気抵抗やマルチフェロイック効果などのMEとは対照的であり、輝コバルト鉱のMEは同一の結晶構造で起こる。われわれの発見は、MEとNTEを実現するための新しい方法を示しており、それは新しい技術に応用されるかもしれない。

論文

Formation of $$alpha$$ clusters in dilute neutron-rich matter

田中 純貴*; Yang, Z.*; Typel, S.*; 足立 智*; Bai, S.*; van Beek, P.*; Beaumel, D.*; 藤川 祐輝*; Han, J.*; Heil, S.*; et al.

Science, 371(6526), p.260 - 264, 2021/01

 被引用回数:30 パーセンタイル:99.14(Multidisciplinary Sciences)

$$alpha$$ノックアウト反応を用いることで、中性子過剰な錫同位体の核表面での$$alpha$$クラスター形成を実験的に確かめた。実験で得られた、質量数とともに単調に減少するノックアウト断面積は理論による予言と非常に良く一致し、$$alpha$$クラスター形成率と中性子スキン厚との関係を示唆している。

論文

International network of nuclear structure and decay data evaluators

Dimitriou, P.*; Basunia, S*; Bernstein, L.*; Chen, J.*; Elekes, Z.*; Huang, X.*; Hurst, A.*; 飯村 秀紀; Jain, A. K.*; Kelley, J.*; et al.

EPJ Web of Conferences, 239, p.15004_1 - 15004_4, 2020/09

BB2020-0008.pdf:0.34MB

 被引用回数:0 パーセンタイル:0.1

評価済み核構造データファイル(Evaluated Nuclear Structure Data File: ENSDF)は、原子核構造と崩壊に関する様々な実験データを全ての核種について集めて、それらの実験データの評価値を与えてある世界唯一のデータファイルである。ENSDFは定期的に更新されており、そのための評価作業は各国の評価者で分担している。評価作業を速やかに行うために、IAEAの援助の下に評価者の国際的なネットワークが組織されている。この発表では、ネットワークの最近の活動のうち、ENSDFの処理コードの開発、測定が必要とされているデータのリストの作成、インターネット版核図表の利用の拡充などについて報告する。また、核構造・崩壊データの需要が増大しているにもかかわらず、評価者が減っている問題についても述べる。

論文

Cooperative deformation in high-entropy alloys at ultralow temperatures

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

Science Advances (Internet), 6(13), p.eaax4002_1 - eaax4002_8, 2020/03

 被引用回数:123 パーセンタイル:99.12(Multidisciplinary Sciences)

High-entropy alloys exhibit exceptional mechanical properties at cryogenic temperatures, due to the activation of twinning in addition to dislocation slip. The coexistence of multiple deformation pathways raises an important question regarding how individual deformation mechanisms compete or synergize during plastic deformation. Using in situ neutron diffraction, we demonstrate the interaction of a rich variety of deformation mechanisms in high-entropy alloys at 15 K, which began with dislocation slip, followed by stacking faults and twinning, before transitioning to inhomogeneous deformation by serrations. Quantitative analysis showed that the cooperation of these different deformation mechanisms led to extreme work hardening. The low stacking fault energy plus the stable face-centered cubic structure at ultralow temperatures, enabled by the high-entropy alloying, played a pivotal role bridging dislocation slip and serration.

論文

Fine structure in the $$alpha$$ decay of $$^{223}$$U

Sun, 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:10 パーセンタイル:80.2(Astronomy & Astrophysics)

Fine structure in the $$alpha$$ decay of $$^{223}$$U was observed in the fusion-evaporation reaction $$^{187}$$Re($$^{40}$$Ar,p3n) by using fast digital pulse processing technique. Two $$alpha$$-decay branches of $$^{223}$$U feeding the ground state and 244 keV excited state of $$^{219}$$Th were identified by establishing the decay chain $$^{223}$$U$$rightarrow$$$$^{219}$$Th$$rightarrow$$$$^{215}$$Ra$$rightarrow$$$$^{211}$$Rn. The $$alpha$$-particle energy for the ground-state to ground-state transition of $$^{223}$$U was determined to be 8993(17) keV, 213 keV higher than the previous value, the half-life was updated to be 62$$^{+14}_{-10} mu$$s. Evolution of nuclear structure for $$N$$=131 even-$$Z$$ isotones from Po to U was discussed in the frameworks of nuclear mass and reduced $$alpha$$-decay width, a weakening octupole deformation in the ground state of $$^{223}$$U relative to its lighter isotones $$^{219}$$Ra and $$^{211}$$Th was suggested.

論文

Determination of fusion barrier distributions from quasielastic scattering cross sections towards superheavy nuclei synthesis

田中 泰貴*; 成清 義博*; 森田 浩介*; 藤田 訓裕*; 加治 大哉*; 森本 幸司*; 山木 さやか*; 若林 泰生*; 田中 謙伍*; 武山 美麗*; et al.

Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01

 被引用回数:16 パーセンタイル:73.53(Physics, Multidisciplinary)

ガス充填型反跳生成核分離装置GARISを用いて$$^{48}$$Ca + $$^{208}$$Pb, $$^{50}$$Ti + $$^{208}$$Pb, $$^{48}$$Ca + $$^{248}$$Cm反応系における準弾性散乱断面積の励起関数を測定した。これらのデータから融合障壁分布を導出し、チャンネル結合計算と比較した。$$^{48}$$Ca + $$^{208}$$Pb及び$$^{50}$$Ti + $$^{208}$$Pb反応の障壁分布のピークエネルギーはそれらの反応系における2中性子蒸発断面積のピークエネルギーと良く一致し、一方$$^{48}$$Ca + $$^{248}$$Cm反応の障壁分布のピークエネルギーは4中性子蒸発断面積のピークエネルギーより少し下に現れることが判った。この結果は超重核合成の際の最適ビームエネルギーの予測に役立つ情報を与える。

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