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論文

Lattice study of SU(2) gauge theory coupled to four adjoint Higgs fields

Catumba, G.*; 平口 敦基; Hou, W.-S.*; Jansen, K.*; Kao, Y.-J.*; David Lin, C.-J.*; Ramos, A.*; Sarkar, M.*

Physical Review Research (Internet), 6(4), p.043172_1 - 043172_12, 2024/11

様々な表現の物質場と結合するゲージ理論は、物理学の様々な分野で重要な役割を果たしている。最近、銅酸化物超伝導体の最適ドーピング近傍の興味深い擬ギャップ相のいくつかの側面が、発現したSU(2)ゲージ対称性によって説明できるかもしれないことが提案された。ホールドーピングによる転移付近では、4つの随伴スカラー場と結合した(2+1)次元SU(2)ゲージ理論を構築することができ、異なる破れた対称性を持つ様々な相が存在する豊かな相図を与える。我々は、ハイブリッドモンテカルロ法を用いて、ユークリッド格子上でこのモデルの相図を研究した。その結果、これまでの平均場の研究で予言されていたように、対称性が破れた複数の相が存在することがわかった。4点相互作用によって、摂動論の範囲ではこの理論のSU(2)ゲージ対称性はU(1)か$$mathbb{Z}_2$$に分解される。さらに、我々はこの理論における閉じ込め-非閉じ込め転移を評価し、我々が研究した格子体積の範囲では、どちらの破れた相も非閉じ込め相であることを見いだした。しかしながら、ポリヤコフループの振る舞いには2つの相で顕著な違いがあることがわかった。

論文

Study of 3-dimensional SU(2) gauge theory with adjoint Higgs as a model for cuprate superconductors

Catumba, G.*; 平口 敦基; W.-S. Hou, G.*; Jansen, K.*; Kao, Y.-J.*; David Lin, C.-J.*; Ramos, A.*; Sarkar, M.*

Proceedings of Science (Internet), 453, p.362_1 - 362_7, 2024/11

本研究では、最近Sachdevらによって最適ドーピング付近の銅酸化物超伝導体の物理を説明するために提案された、随伴表現の4つのヒッグス場を持つ3次元SU(2)ゲージ理論を議論する。この理論の閉じ込め相は通常のフェルミ液体相に対応し、ヒッグス相は銅酸化物の擬ギャップ相に対応しており、我々はハイブリッドモンテカルロ法を用いて理論の相図を調査した。我々は、先行研究の平均場での計算に定性的に従う様々な相の存在を発見し、銅酸化物におけるそれらの役割について議論する。さらに、閉じ込め非閉じ込め相転移を調べるためにポリヤコフループの振る舞いを調べ、ヒッグス相が安定な非閉じ込め相を持つことを見いだした。

論文

Lattice investigation of the general Two Higgs Doublet Model with $$SU(2)$$ gauge fields

Catumba, G.*; 平口 敦基; W.-S. Hou, G.*; Jansen, K.*; Kao, Y.-J.*; David Lin, C.-J.*; Ramos, A.*; Sarkar, M.*

Proceedings of Science (Internet), 453, p.87_1 - 87_9, 2024/11

本研究では、$$SU(2)$$ゲージ場と相互作用する一般的な2ヒッグスダブレット模型を格子ゲージ理論で議論する。秩序変数の代わりとしてゲージ不変の大域的観測量を計算することにより、この模型の相図を調べた。それぞれの相において、裸の結合定数の組み合わせや対称性の破れのパターンを変えて理論のスカラー粒子およびベクトルボソン粒子の質量の評価を行なった。またスケール設定と走るゲージ結合定数の決定は、ウィルソンフロウの計算によって行なった。

論文

Onset of collectivity for argon isotopes close to $$N=32$$

Linh, B. D.*; Corsi, A.*; Gillibert, A.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Duguet, T.*; G$'o$mez-Ramos, M.*; Holt, J. D.*; Hu, B. S.*; et al.

Physical Review C, 109(3), p.034312_1 - 034312_15, 2024/03

 被引用回数:2 パーセンタイル:58.81(Physics, Nuclear)

理化学研究所RIビームファクトリーにて中性子過剰核$$^{50}$$Arビームからの1中性子ノックアウト反応実験を行い、$$^{49}$$Arのエネルギー準位および分光学的因子を導出した。特に、第一励起状態の$$1/2^-$$への分光学的因子が大きいことから、始状態の$$^{50}$$Arの基底状態において中性子が$$p_{1/2}$$軌道を多く占めていることがわかった。これは、中性子数32がよい魔法数として知られる$$^{52}$$Caとは異なった性質であり、カルシウムからアルゴンへと陽子が2個減ることで閉殻構造が大きく崩れることが明らかになった。

論文

First report of geo- and thermochronological results from the Cordillera Central, Luzon, Philippines

中嶋 徹; 末岡 茂; 長田 充弘; Kohn, B. P.*; Ramos, N. T.*; 堤 浩之*; 田上 高広*

Earth, Planets and Space (Internet), 75(1), p.176_1 - 176_11, 2023/12

 被引用回数:1 パーセンタイル:23.38(Geosciences, Multidisciplinary)

本研究では島弧山地における中間質マグマの貫入と隆起・侵食過程を理解する目的で、フィリピン、ルソン島の中央コルディエラ山地に地質・熱年代測定を適用した。ジルコンU-Pb年代は32.54$$pm$$0.70から6.11$$pm$$0.15(2SE)Maであり、これは第三紀火成活動に伴う中・上部地殻における中間質マグマの断続的な貫入イベントを反映している。ジルコンのフィッション・トラック(ZFT)年代は35.63$$pm$$2.17から6.91$$pm$$0.36(2SE)Maであり、それぞれの試料採取地点におけるジルコンU-Pb年代と対比される。これは中間質マグマが貫入後、即座に250$$sim$$350$$^{circ}$$Cまで冷却したことを反映している。一方、ジルコンとアパタイトの(U-Th-Sm)/He(ZHe, AHe)年代はそれぞれ11.71$$pm$$0.36から8.82$$pm$$0.26Maと9.21$$pm$$0.52から0.98$$pm$$0.088(2SE)Maであり、ジルコンのU-Pb年代やZFT年代よりも若い傾向にある。これは各地点における岩石の冷却速度が低温領域において減少したことを示唆する。そのため、ZFT年代は中間質マグマの初期冷却を、AHe年代は隆起・侵食に伴う冷却をそれぞれ反映していると考えられる。AHe年代の地理的分布は、第四紀に中央コルディエラ山地全体がブロック状に隆起したことを示唆している。

論文

Laser-induced creation of antiferromagnetic 180-degree domains in NiO/Pt bilayers

Meer, H.*; Wust, S.*; Schmitt, C.*; Herrgen, P.*; Fuhrmann, F.*; Hirtle, S.*; Bednarz, B.*; Rajan, A.*; Ramos, R.*; Ni$~n$o, M. A.*; et al.

Advanced Functional Materials, 33(21), p.2213536_1 - 2213536_6, 2023/05

 被引用回数:6 パーセンタイル:58.52(Chemistry, Multidisciplinary)

The antiferromagnetic order in heterostructures of NiO/Pt thin films can be modified by optical pulses. After the irradiation with laser light, the optically induced creation of antiferromagnetic domains can be observed by imaging the created domain structure utilizing the X-ray magnetic linear dichroism effect. The effect of different laser polarizations on the domain formation can be studied and used to identify a polarization-independent creation of 180$$^{circ}$$ domain walls and domains with 180$$^{circ}$$ different N$'e$el vector orientation. By varying the irradiation parameters, the switching mechanism can be determined to be thermally induced. This study demonstrates experimentally the possibility to optically create antiferromagnetic domains, an important step towards future functionalization of all optical switching mechanisms in antiferromagnets.

論文

Current-induced crystallisation in a Heusler-alloy-based giant magnetoresistive junction for neuromorphic potentiation

Zhou, Z.*; Frost, W.*; Lloyd, D. C.*; 関 剛斎*; 窪田 崇秀*; Ramos, R.*; 齊藤 英治; 高梨 弘毅; 廣畑 貴文*

Journal of Magnetism and Magnetic Materials, 571, p.170575_1 - 170575_5, 2023/04

 被引用回数:1 パーセンタイル:11.20(Materials Science, Multidisciplinary)

Recent development in neuromorphic computation allows us to achieve low power and highly efficient calculations better than the conventional von Neumann computation. In order to achieve realistic synaptic operation, potentiation to add weighting to strengthen a selected artificial synapse. Such functionality can be achieved by reducing the electrical resistance of the artificial synapse. Recently, a ferromagnetic Heusler alloy used in a magnetoresistive junction has been demonstrated to crystallise via the layer-by-layer mode by introducing an electrical current pulse. In this study, we have extended the current-induced crystallisation to a junction with epitaxially-grown Heusler alloy after post-annealing for crystallisation. By combining this potentiation functionality with the neuromorphic operation, realistic synaptic computation can be developed.

論文

Multiple mechanisms in proton-induced nucleon removal at $$sim$$100 MeV/nucleon

Pohl, T.*; Sun, Y. L.*; Obertelli, A.*; Lee, J.*; G$'o$mez-Ramos, M.*; 緒方 一介*; 吉田 数貴; Cai, B. S.*; Yuan, C. X.*; Brown, B. A.*; et al.

Physical Review Letters, 130(17), p.172501_1 - 172501_8, 2023/04

 被引用回数:12 パーセンタイル:88.25(Physics, Multidisciplinary)

大きなフェルミ面非対称性を持つ陽子過剰な$$^{14}$$O原子核からの100MeV/nucleonでの陽子による陽子・中性子除去反応について報告した。この結果は、quasi-freeノックアウト反応、非弾性散乱、核子移行反応を含む複数の反応機構の定量的寄与を初めて示すものである。このようなエネルギー領域では通常無視される非弾性散乱と核子移行の寄与が、弱束縛陽子と強束縛中性子の除去反応断面積にそれぞれ約50%と30%寄与していることが示された。

論文

Magnetic sensitivity distribution of Hall devices in antiferromagnetic switching experiments

Schreiber, F.*; Meer, H.*; Schmitt, C.*; Ramos, R.*; 齊藤 英治; Baldrati, L.*; Kl$"a$ui, M.*

Physical Review Applied (Internet), 16(6), p.064023_1 - 064023_9, 2021/12

 被引用回数:4 パーセンタイル:24.33(Physics, Applied)

We analyze the complex impact of the local magnetic spin texture on the transverse Hall-type voltage in device structures utilized to measure magnetoresistance effects. We find a highly localized and asymmetric magnetic sensitivity in the eight-terminal geometries that are frequently used in current-induced switching experiments, for instance, to probe antiferromagnetic materials. Using current-induced switching of antiferromagnetic NiO/Pt as an example, we estimate the change in the spin Hall magnetoresistance signal associated with switching events based on the domain-switching patterns observed via direct imaging. This estimate correlates with the actual electrical data after subtraction of a nonmagnetic contribution. Here, the consistency of the correlation across three measurement geometries with fundamentally different switching patterns strongly indicates a magnetic origin of the measured and analyzed electrical signals.

論文

Investigation of the ground-state spin inversion in the neutron-rich $$^{47,49}$$Cl isotopes

Linh, B. D.*; Corsi, A.*; Gillibert, A.*; Obertelli, A.*; Doornenbal, P.*; Barbieri, C.*; Chen, S.*; Chung, L. X.*; Duguet, T.*; G$'o$mez-Ramos, M.*; et al.

Physical Review C, 104(4), p.044331_1 - 044331_16, 2021/10

AA2021-0468.pdf:1.29MB

 被引用回数:10 パーセンタイル:72.28(Physics, Nuclear)

理化学研究所のRIビームファクトリーにて中性子過剰$$^{47,49}$$Clの励起状態を$$^{50}$$Arからのノックアウト反応によって生成し、脱励起ガンマ線からそのエネルギー準位を測定した。また、陽子ノックアウトの運動量分布から$$^{49}$$Clの基底状態が$$3/2^+$$であることがわかった。その結果を大規模殻模型計算およびいくつかの第一原理計算と比較した。$$^{47,49}$$Cl同位体の基底状態および第一励起状態は、計算で用いた相互作用に敏感であることがわかった。それは、陽子の一粒子エネルギーと四重極集団運動との複雑な結合によるためであると考えられる。

論文

Observation of nuclear-spin Seebeck effect

吉川 貴史*; Reitz, D.*; 伊藤 宏陽*; 巻内 崇彦*; 杉本 宜陽*; 恒川 翔*; 大門 俊介*; 大柳 洸一*; Ramos, R.*; 高橋 三郎*; et al.

Nature Communications (Internet), 12, p.4356_1 - 4356_7, 2021/07

 被引用回数:23 パーセンタイル:84.33(Multidisciplinary Sciences)

Thermoelectric effects have been applied to power generators and temperature sensors that convert waste heat into electricity. The effects, however, have been limited to electrons to occur, and inevitably disappear at low temperatures due to electronic entropy quenching. Here, we report thermoelectric generation caused by nuclear spins in a solid: nuclear-spin Seebeck effect. The sample is a magnetically ordered material MnCO$$_3$$ having a large nuclear spin $$(I=5/2)$$ of $$^{55}$$Mn nuclei and strong hyperfine coupling, with a Pt contact. In the system, we observe low-temperature thermoelectric signals down to 100 mK due to nuclear-spin excitation. Our theoretical calculation in which interfacial Korringa process is taken into consideration quantitatively reproduces the results. The nuclear thermoelectric effect demonstrated here offers a way for exploring thermoelectric science and technologies at ultralow temperatures.

論文

Evaluation of edge domains in giant magnetoresistive junctions

Frost, W.*; 関 剛斎*; 窪田 崇秀*; Ramos, R.*; 齊藤 英治; 高梨 弘毅*; 廣畑 貴文*

Applied Physics Letters, 118(17), p.172405_1 - 172405_5, 2021/04

 被引用回数:1 パーセンタイル:4.62(Physics, Applied)

We demonstrate that the spin-Seebeck effect can be used to estimate the volume of edge domains formed in a giant magnetoresistive (GMR) device. The thermal gradient induced by Joule heating can be harnessed by the addition of a ferromagnetically insulating channel of Fe$$_2$$O$$_3$$ on the sides of the GMR pillar. This generates a spin wave in Fe$$_2$$O$$_3$$, which couples with the free-layer edge magnetization and controls the reversal of the ferromagnetic layers in one direction only, increasing the current density from $$(1.1pm0.1)times10^7$$ A/cm$$^2$$ to $$(7.0pm0.5)times10^7$$ A/cm$$^2$$. By simple assumption, we estimate the effect of the edge domain on magnetization reversal to be $$10%-15%$$ by spin-transfer torque.

論文

Experimental evidence for common driving effects in low-energy fission from sublead to actinides

Schmitt, C.*; Lemasson, A.*; Schmidt, K.-H.*; Jhingan, A.*; Biswas, S.*; Kim, Y. H.*; Ramos, D.*; Andreyev, A. N.; Curien, D.*; Ciemala, M.*; et al.

Physical Review Letters, 126(13), p.132502_1 - 132502_6, 2021/04

 被引用回数:23 パーセンタイル:81.57(Physics, Multidisciplinary)

Isotopic distributions of fragments from fission of the neutron-deficient $$^{178}$$Hg nuclide are reported. This experimental observable is obtained for the first time in the region around lead using an innovative approach based on inverse kinematics and the coincidence between the large acceptance magnetic spectrometer VAMOS++ and a new detection arm close to the target. The average fragment $$N/Z$$ ratio and prompt neutron $$Mn$$ multiplicity are derived and compared with current knowledge from actinide fission. A striking consistency emerges, revealing the unexpected dominant role of the proton subsystem with atomic number between the $$Z$$ = 28 and 50 magic numbers. The origin of nuclear charge polarization in fission and fragment deformation at scission are discussed.

論文

Direct imaging of current-induced antiferromagnetic switching revealing a pure thermomagnetoelastic switching mechanism in NiO

Meer, H.*; Schreiber, F.*; Schmitt, C.*; Ramos, R.*; 齊藤 英治; Gomonay, O.*; Sinova, J.*; Baldrati, L.*; Kl$"a$ui, M.*

Nano Letters, 21(1), p.114 - 119, 2021/01

 被引用回数:64 パーセンタイル:95.84(Chemistry, Multidisciplinary)

We unravel the origin of current-induced magnetic switching of insulating antiferromagnet/heavy metal systems. We utilize concurrent transport and magneto-optical measurements to image the switching of antiferromagnetic domains in specially engineered devices of NiO/Pt bilayers. Different electrical pulsing and device geometries reveal different final states of the switching with respect to the current direction. We can explain these through simulations of the temperature-induced strain, and we identify the thermomagnetoelastic switching mechanism combined with thermal excitations as the origin, in which the final state is defined by the strain distributions and heat is required to switch the antiferromagnetic domains. We show that such a potentially very versatile noncontact mechanism can explain the previously reported contradicting observations of the switching final state, which were attributed to spin-orbit torque mechanisms.

論文

Observation of quantum interference conductance fluctuations in metal rings with strong spin-orbit coupling

Ramos, R.*; 巻内 崇彦*; 吉川 貴史*; 大門 俊介*; 大柳 洸一*; 齊藤 英治

Applied Physics Letters, 117(24), p.242402_1 - 242402_5, 2020/12

 被引用回数:1 パーセンタイル:3.97(Physics, Applied)

We investigated the magnetotransport properties of mesoscopic platinum nanostructures (wires and rings) with sub-100 nm lateral dimensions at very low temperatures. Despite the strong spin-orbit interaction in platinum, oscillation of the conductance as a function of the external magnetic field due to quantum interference effects was found to appear. The oscillation was decomposed into Aharonov-Bohm periodic oscillations and aperiodic fluctuations of the conductance due to a magnetic flux piercing the loop of the ring and the metal wires forming the nanostructures, respectively. We also investigated the magnetotransport under different bias currents to explore the interplay between electron phase coherence and spin accumulation effects in strong spin-orbit conductors.

論文

Simultaneous determination of neutron-induced fission and radiative capture cross sections from decay probabilities obtained with a surrogate reaction

P$'e$rez S$'a$nchez, R.*; Jurado, B.*; M$'e$ot, V.*; Roig, O.*; Dupuis, M.*; Bouland, O.*; Denis-Petit, D.*; Marini, P.*; Mathieu, L.*; Tsekhanovich, I.*; et al.

Physical Review Letters, 125(12), p.122502_1 - 122502_5, 2020/09

 被引用回数:21 パーセンタイル:70.42(Physics, Multidisciplinary)

Reliable neutron-induced-reaction cross sections of unstable nuclei are essential for nuclear astrophysics and applications but their direct measurement is often impossible. The surrogate-reaction method is one of the most promising alternatives to access these cross sections. In this work, we successfully applied the surrogate-reaction method to infer for the first time both the neutron-induced fission and radiative capture cross sections of $$^{239}$$Pu in a consistent manner from a single measurement. This was achieved by combining simultaneously measured fission and $$gamma$$-emission probabilities for the $$^{240}$$Pu($$^{4}$$He, $$^{4}$$He') surrogate reaction with a calculation of the angular-momentum and parity distributions populated in this reaction. While other experiments measure the probabilities for some selected $$gamma$$-ray transitions, we measure the $$gamma$$-emission probability. This enlarges the applicability of the surrogate-reaction method.

論文

Concurrent magneto-optical imaging and magneto-transport readout of electrical switching of insulating antiferromagnetic thin films

Schreiber, F.*; Baldrati, L.*; Schmitt, C.*; Ramos, R.*; 齊藤 英治; Lebrun, R.*; Kl$"a$ui, M.*

Applied Physics Letters, 117(8), p.082401_1 - 082401_5, 2020/08

 被引用回数:29 パーセンタイル:81.04(Physics, Applied)

We demonstrate stable and reversible current induced switching of large-area ($$>$$100 $$mu$$m$$^2$$) antiferromagnetic domains in NiO/Pt by performing concurrent transport and magneto-optical imaging measurements in an adapted Kerr microscope. By correlating the magnetic images of the antiferromagnetic domain changes and magneto-transport signal response in these current-induced switching experiments, we disentangle magnetic and non-magnetic contributions to the transport signal. Our table-top approach establishes a robust procedure to subtract the non-magnetic contributions in the transport signal and extract the spin-Hall magnetoresistance response associated with the switching of the antiferromagnetic domains, enabling one to deduce details of the antiferromagnetic switching from simple transport measurements.

論文

Efficient spin torques in antiferromagnetic CoO/Pt quantified by comparing field- and current-induced switching

Baldrati, L.*; Schmitt, C.*; Gomonay, O.*; Lebrun, R.*; Ramos, R.*; 齊藤 英治; Sinova, J.*; Kl$"a$ui, M.*

Physical Review Letters, 125(7), p.077201_1 - 077201_6, 2020/08

 被引用回数:42 パーセンタイル:90.01(Physics, Multidisciplinary)

We achieve current-induced switching in collinear insulating antiferromagnetic CoO/Pt, with fourfold in-plane magnetic anisotropy. This is measured electrically by spin Hall magnetoresistance and confirmed by the magnetic field-induced spin-flop transition of the CoO layer. By applying current pulses and magnetic fields, we quantify the efficiency of the acting current-induced torques and estimate a current-field equivalence ratio of $$4times10^{-11}$$ TA$$^{-1}$$m$$^2$$. The N$'{e}$el vector final state $$(mathbf{n}perp mathbf{j})$$ is in line with a thermomagnetoelastic switching mechanism for a negative magnetoelastic constant of the CoO.

論文

Sequential nature of ($$p,3p$$) two-proton knockout from neutron-rich nuclei

Frotscher, A.*; G$'o$mez-Ramos, M.*; Obertelli, A.*; Doornenbal, P.*; Authelet, G.*; 馬場 秀忠*; Orlandi, R.; 他86名*

Physical Review Letters, 125(1), p.012501_1 - 012501_7, 2020/07

 被引用回数:10 パーセンタイル:57.53(Physics, Multidisciplinary)

Twenty-one two-proton ($$p,3p$$) knock-out cross sections of neutron-rich radioactive isotopes were measured in inverse kinematics using the MINOS time-projection chamber at RIBF, RIKEN. The proton angular distributions, measured for the first time, reveal that the reaction kinematics of the ($$p,3p$$) reaction is consistent with sequential proton collisions within the projectile nucleus.

論文

Absence of evidence of spin transport through amorphous Y$$_3$$Fe$$_5$$O$$_{12}$$

Gomez-Perez, J. M.*; 大柳 洸一*; 八尋 黎明*; Ramos, R.*; Hueso, L. E.*; 齊藤 英治; Casanova, F.*

Applied Physics Letters, 116(3), p.032401_1 - 032401_5, 2020/01

 被引用回数:10 パーセンタイル:47.20(Physics, Applied)

We probe the current-induced magnetic switching of insulating antiferromagnet-heavy-metal systems, by electrical spin Hall magnetoresistance measurements and direct imaging, identifying a reversal occurring by domain wall (DW) motion. We observe switching of more than one-third of the antiferromagnetic domains by the application of current pulses. Our data reveal two different magnetic switching mechanisms leading together to an efficient switching, namely, the spin-current induced effective magnetic anisotropy variation and the action of the spin torque on the DWs.

42 件中 1件目~20件目を表示