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論文

Singular continuous and nonreciprocal phonons in quasicrystal AlPdMn

松浦 直人*; Zhang, J.*; 上村 祥史*; 古府 麻衣子; 枝川 圭一*

Physical Review Letters, 133(13), p.136101_1 - 136101_5, 2024/09

 被引用回数:1

In quasicrystals lacking translational symmetry but having highly ordered structures, understanding how phonons propagate in their aperiodic lattices remains an unsolved issue. We present an inelastic neutron scattering study on acoustic phonon modes of icosahedral quasicrystal AlPdMn, revealing hierarchical pseudo-gap structure in low-energy acoustic modes. Additionally, phonon intensities are asymmetric in energy and wave vectors with respect to the Bragg peak, indicating characteristic nonreciprocal phonon propagation in quasicrystals.

論文

Antiferromagnetism and phase stability of CrMnFeCoNi high-entropy alloy

Zhu, L.*; He, H.*; Naeem, M.*; Sun, X.*; Qi, J.*; Liu, P.*; Harjo, S.; 中島 健次; Li, B.*; Wang, X.-L.*

Physical Review Letters, 133(12), p.126701_1 - 126701_6, 2024/09

It has long been suspected that magnetism could play a vital role in the phase stability of multi- component high-entropy alloys. However, the nature of the magnetic order, if any, has remained elusive. Here, by using elastic and inelastic neutron scattering, we demonstrate evidence of antiferromagnetic order below $$sim$$80 K and strong spin fluctuations persisting to room temperature in a single-phase face-centered cubic (fcc) CrMnFeCoNi high-entropy alloy. Despite the chemical complexity, the magnetic structure in CrMnFeCoNi can be described as $$gamma$$-Mn-like, with the magnetic moments confined in alternating (001) planes and pointing toward the $$langle$$111$$rangle$$ direction. Combined with first-principles calculation results, it is shown that the antiferromagnetic order and spin fluctuations help stabilized the fcc phase in CrMnFeCoNi high-entropy alloy.

論文

Acoustomagnonic spin Hall effect in honeycomb antiferromagnets

佐野 涼太郎*; 大湊 友也*; 松尾 衛

Physical Review Letters, 132(23), p.236302_1 - 236302_9, 2024/06

 被引用回数:2 パーセンタイル:87.91(Physics, Multidisciplinary)

We propose an ac intrinsic magnon spin Hall current driven by surface acoustic waves as a novel probe for such antiferromagnets. Our results pave the way towards mechanical detection and manipulation of the magnetic order in two-dimensional antiferromagnets.

論文

Chirality-induced phonon-spin conversion at an interface

船戸 匠*; 松尾 衛; 加藤 岳生*

Physical Review Letters, 132(23), p.236201_1 - 236201_7, 2024/06

 被引用回数:2 パーセンタイル:72.81(Physics, Multidisciplinary)

Our results clearly illustrate the microscopic origin of spin current generation by chiral phonons and may lead to a breakthrough in the development of spintronic devices without heavy elements.

論文

High-temperature atomic diffusion and specific heat in quasicrystals

永井 佑紀; 岩崎 祐昂*; 北原 功一*; 高際 良樹*; 木村 薫*; 志賀 基之

Physical Review Letters, 132(19), p.196301_1 - 196301_6, 2024/05

 被引用回数:1 パーセンタイル:72.81(Physics, Multidisciplinary)

準結晶とは、高次元超格子の3次元空間への射影として理解できる周期性のない物質である。高温における比熱の上昇は、準結晶の高次元性を反映した現象として二十年以上議論されてきた。しかし、準結晶やその近似結晶の比熱の理論計算はその原子構造の複雑さから困難であった。実験と理論の橋渡しを行うため、最先端の機械学習分子動力学法を用いて、比熱の理論計算を試みた。そして、Al-Pd-Ru準結晶とその近似結晶において、実験グループとの共同研究により、実験で異常高温比熱が現れること、理論で同様の現象が再現できること、の二つを確かめた。そして、異常高温比熱が現れる温度領域においては、アルミニウム原子が不連続に飛び移りながら拡散していくことがわかった。そして、その拡散の経路は6次元超原子の揺らぎとして理解することができることを明らかにした。

論文

Longitudinal spin fluctuations driving field-reinforced superconductivity in UTe$$_2$$

徳永 陽; 酒井 宏典; 神戸 振作; Opletal, P.; 常盤 欣文; 芳賀 芳範; 北川 俊作*; 石田 憲二*; 青木 大*; Knebel, G.*; et al.

Physical Review Letters, 131(22), p.226503_1 - 226503_7, 2023/12

 被引用回数:6 パーセンタイル:80.90(Physics, Multidisciplinary)

Our measurements of $$^{125}$$Te NMR relaxations reveal an enhancement of electronic spin fluctuations above $$mu_0H^*sim15$$~T, leading to their divergence in the vicinity of the metamagnetic transition at $$mu_0H_mapprox35$$~T, below which field-reinforced superconductivity appears when a magnetic field ($$H$$) is applied along the crystallographic $$b$$ axis. The NMR data evidence that these fluctuations are dominantly longitudinal, providing a key to understanding the peculiar superconducting phase diagram in $$H|b$$, where such fluctuations enhance the pairing interactions.

論文

Acoustically driven magnon-phonon coupling in a layered antiferromagnet

Lyons, T. P.*; Puebla, J.*; 山本 慧; Deacon, R. S.*; Hwang, Y.*; 石橋 幸治*; 前川 禎通*; 大谷 義近*

Physical Review Letters, 131(19), p.196701_1 - 196701_6, 2023/11

 被引用回数:8 パーセンタイル:87.40(Physics, Multidisciplinary)

Harnessing the causal relationships between mechanical and magnetic properties of van der Waals materials presents a wealth of untapped opportunity for scientific and technological advancement, from precision sensing to novel memories. This can, however, only be exploited if the means exist to efficiently interface with the magnetoelastic interaction. Here, we demonstrate acoustically-driven spin-wave resonance in a crystalline antiferromagnet, chromium trichloride, via surface acoustic wave irradiation. The resulting magnon-phonon coupling is found to depend strongly on sample temperature and external magnetic field orientation, and displays a high sensitivity to extremely weak magnetic anisotropy fields in the few mT range. Our work demonstrates a natural pairing between power-efficient strain-wave technology and the excellent mechanical properties of van der Waals materials, representing a foothold towards widespread future adoption of dynamic magneto-acoustics.

論文

Validation of the $$^{10}$$Be ground-state molecular structure using $$^{10}$$Be($$p,palpha$$)$$^{6}$$He triple differential reaction cross-section measurements

Li, P. J.*; Beaumel, D.*; Lee, J.*; Assi$'e$, M.*; Chen, S.*; Franchoo, S.*; Gibelin, J.*; Hammache, F.*; Harada, T.*; 延与 佳子*; et al.

Physical Review Letters, 131(21), p.212501_1 - 212501_7, 2023/11

 被引用回数:6 パーセンタイル:75.19(Physics, Multidisciplinary)

$$^{10}$$Beのクラスター構造を($$p,palpha$$)反応を用いて調査した。三重微分断面積が実験的に測定され、Tohsaki-Horiuchi-Schuck-R$"o$pke波動関数の方法や反対称化分子動力学を用いた歪曲波インパルス近似計算と比較した。実験データと理論計算の顕著な一致が確認され、$$^{10}$$Beの比較的コンパクトな分子状態を確認した。

論文

Valley-selective phonon-magnon scattering in magnetoelastic superlattices

Liao, L.*; Puebla, J.*; 山本 慧; Kim, J.*; 前川 禎通*; Hwang, Y.*; Ba, Y.*; 大谷 義近*

Physical Review Letters, 131(17), p.176701_1 - 176701_6, 2023/10

 被引用回数:6 パーセンタイル:80.90(Physics, Multidisciplinary)

Phonons and magnons are engineered by periodic potential landscapes in phononic and magnonic crystals, and their combined studies may enable valley phonon transport tunable by the magnetic field. Through nonreciprocal surface acoustic wave transmission, we demonstrate valley-selective phonon-magnon scattering in magnetoelastic superlattices. The lattice symmetry and the out-of-plane magnetization component control the sign of nonreciprocity. The phonons in the valleys play a crucial role in generating nonreciprocal transmission by inducing helical strains that couple with the magnons. The transmission spectra show a nonreciprocity peak near a transmission gap, matching the phononic band structure. Our results open the way for manipulating valley phonon transport through periodically varying magnon-phonon coupling.

論文

One fixed point can hide another one; Nonperturbative behavior of the tetracritical fixed point of O($$N$$) models at large $$N$$

藪中 俊介; Delamotte, B.*

Physical Review Letters, 130(26), p.261602_1 - 261602_6, 2023/06

 被引用回数:0 パーセンタイル:0.00(Physics, Multidisciplinary)

We show that at $$N=infty$$ and below its upper critical dimension, $$d<d_{rm up}$$, the critical and tetracritical behaviors of the O$$(N)$$ models are associated with the same renormalization group fixed point (FP) potential. Only their derivatives make them different with the subtleties that taking their $$Ntoinfty$$ limit and deriving them do not commute and that two relevant eigenperturbations show singularities. This invalidates both the $$epsilon$$- and the $$1/N$$- expansions. We also show how the Bardeen-Moshe-Bander line of tetracritical FPs at $$N=infty$$ and $$d=d_{rm up}$$ can be understood from a finite-$$N$$ analysis.

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:9 パーセンタイル:89.52(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

Field induced multiple superconducting phases in UTe$$_2$$ along hard magnetic axis

酒井 宏典; 常盤 欣文; Opletal, P.; 木俣 基*; 淡路 智*; 佐々木 孝彦*; 青木 大*; 神戸 振作; 徳永 陽; 芳賀 芳範

Physical Review Letters, 130(19), p.196002_1 - 196002_6, 2023/05

 被引用回数:16 パーセンタイル:96.61(Physics, Multidisciplinary)

$$T_{rm c}$$=2.1Kのウラン2テルル化物単結晶における超伝導相図を磁気困難軸である結晶$$b$$軸方向に磁場をかけて調べた。電気抵抗と交流帯磁率を同時に測定した結果、低磁場超伝導(LFSC)相と高磁場超伝導(HFSC)相が、対照的な磁場-角度依存性をもつことがわかった。結晶の純良性が上がったことにより、LFSC相の上部臨界磁場は上昇したものの、HFSC相が現れる特徴磁場$$H^{ast}$$は、単結晶の純良性に関わらず、15Tと一定であることがわかった。また、$$H^{ast}$$近傍のLFSC相内に、弱い渦糸ピン留め力で特徴づけられる中間超伝導相を示唆する新たな相線の形跡を捉えた。

論文

Proof-of-principle experiment for testing strong-field quantum electrodynamics with exotic atoms; High precision X-ray spectroscopy of muonic neon

奥村 拓馬*; 橋本 直; 他40名*

Physical Review Letters, 130(17), p.173001_1 - 173001_7, 2023/04

 被引用回数:6 パーセンタイル:84.64(Physics, Multidisciplinary)

To test bound-state quantum electrodynamics (BSQED) in the strong-field regime, we have performed high-precision X-ray spectroscopy of the 5$$g$$-4$$f$$ and 5$$f$$-4$$d$$ transitions (BSQED contribution of 2.4 eV and 5.2 eV, respectively) of muonic neon atoms in the low-pressure gas phase without bound electrons. Muonic atoms have been recently proposed as an alternative to few-electron high-Z ions for BSQED tests by focusing on circular Rydberg states where nuclear contributions are negligibly small. We determined the $$5g_{9/2}$$-$$4f_{7/2}$$ transition energy to be 6297.08 $$pm$$ 0.04 (stat.) $$pm$$ 0.13 (syst.) eV using superconducting transition-edge sensor microcalorimeters (5.2-5.5 eV FWHM resolution), which agrees well with the most advanced BSQED theoretical prediction of 6297.26 eV.

論文

Breaking down the magnonic Wiedemann-Franz law in the hydrodynamic regime

佐野 涼太郎*; 松尾 衛

Physical Review Letters, 130(16), p.166201_1 - 166201_7, 2023/04

 被引用回数:1 パーセンタイル:34.43(Physics, Multidisciplinary)

Recent experiments have shown an indication of a hydrodynamic magnon behavior in ultrapure ferromagnetic insulators; however, its direct observation is still lacking. Here, we derive a set of coupled hydrodynamic equations and study the thermal and spin conductivities for such a magnon fluid. We reveal the drastic breakdown of the magnonic Wiedemann-Franz law as a hallmark of the hydrodynamics regime, which will become key evidence for the experimental realization of an emergent hydrodynamic magnon behavior. Therefore, our results pave the way toward the direct observation of magnon fluids.

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:7 パーセンタイル:87.40(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

Magnonic Casimir effect in ferrimagnets

仲田 光樹; 鈴木 渓

Physical Review Letters, 130(9), p.096702_1 - 096702_6, 2023/03

 被引用回数:5 パーセンタイル:80.90(Physics, Multidisciplinary)

量子場の真空ゆらぎによって創発されるカシミア効果は、古典力学には対応物が存在しないという意味において真に量子力学的な効果である。しかし、カシミア効果はこれまでフォトン(光子)を舞台に研究されており、磁性体中でのカシミア効果、特にそのカシミアエネルギーの膜厚依存性については十分な理解は得られていない。そこで本研究では格子場の理論の観点から、磁性絶縁体中のスピン波を量子化したマグノンに着目し、マグノン量子場により創発されるカシミア効果「マグノン・カシミア効果」及びその膜厚依存性を明らかにする。更に反強磁性絶縁体だけでなくフェリ磁性絶縁体(例:YIG)においてもマグノン・カシミア効果が創発することを示し、スピントロニクス分野で中心的な役割を担うYIGがカシミア効果の工学的応用を目指すカシミアエンジニアリング分野にとっても絶好の舞台であることを明らかにする。本研究は、マグノン・カシミアエンジニアリングの基礎学理の構築に大きく貢献することが期待される。

論文

Nonlinear magnon polaritons

Lee, O.*; 山本 慧; 埋田 真樹; Zollitsch, C. W.*; Elyasi, M.*; 吉川 貴史*; 齊藤 英治; Bauer, G. E. W.*; 紅林 秀和*

Physical Review Letters, 130(4), p.046703_1 - 046703_6, 2023/01

 被引用回数:13 パーセンタイル:93.36(Physics, Multidisciplinary)

We experimentally and theoretically demonstrate that nonlinear spin-wave interactions suppress the hybrid magnon-photon quasiparticle or "magnon polariton" in microwave spectra of an yttrium iron garnet film detected by an on-chip split-ring resonator. We observe a strong coupling between the Kittel and microwave cavity modes in terms of an avoided crossing as a function of magnetic fields at low microwave input powers, but a complete closing of the gap at high powers. The experimental results are well explained by a theoretical model including the three-magnon decay of the Kittel magnon into spin waves. The gap closure originates from the saturation of the ferromagnetic resonance above the Suhl instability threshold by a coherent back reaction from the spin waves.

論文

Study of the $$N=32$$ and $$N=34$$ shell gap for Ti and V by the first high-precision multireflection time-of-flight mass measurements at BigRIPS-SLOWRI

飯村 俊*; Rosenbusch, M.*; 高峰 愛子*; 角田 佑介*; 和田 道治*; Chen, S.*; Hou, D. S.*; Xian, W.*; 石山 博恒*; Yan, S.*; et al.

Physical Review Letters, 130(1), p.012501_1 - 012501_6, 2023/01

 被引用回数:9 パーセンタイル:91.15(Physics, Multidisciplinary)

The atomic masses of $$^{55}$$Sc, $$^{56,58}$$Ti, and $$^{56-59}$$V have been determined using the high-precision multireflection time-of-flight technique. The radioisotopes have been produced at RIKEN's Radioactive Isotope Beam Factory (RIBF) and delivered to the novel designed gas cell and multireflection system, which has been recently commissioned downstream of the ZeroDegree spectrometer following the BigRIPS separator. For $$^{56,58}$$Ti and $$^{56-59}$$V, the mass uncertainties have been reduced down to the order of 10 keV, shedding new light on the $$N=34$$ shell effect in Ti and V isotopes by the first high-precision mass measurements of the critical species $$^{58}$$Ti and $$^{59}$$V. With the new precision achieved, we reveal the nonexistence of the $$N=34$$ empirical two-neutron shell gaps for Ti and V, and the enhanced energy gap above the occupied $$nu$$p$$_{3/2}$$ orbit is identified as a feature unique to Ca. We perform new Monte Carlo shell model calculations including the $$nu$$d$$_{5/2}$$ and $$nu$$g$$_{9/2}$$ orbits and compare the results with conventional shell model calculations, which exclude the $$nu$$g$$_{9/2}$$ and the $$nu$$d$$_{5/2}$$ orbits. The comparison indicates that the shell gap reduction in Ti is related to a partial occupation of the higher orbitals for the outer two valence neutrons at $$N = 34$$.

論文

Extended $$p_{3/2}$$ neutron orbital and the $$N = 32$$ shell closure in $$^{52}$$Ca

Enciu, M.*; Liu, H. N.*; Obertelli, A.*; Doornenbal, P.*; Nowacki, F.*; 緒方 一介*; Poves, A.*; 吉田 数貴; Achouri, N. L.*; 馬場 秀忠*; et al.

Physical Review Letters, 129(26), p.262501_1 - 262501_7, 2022/12

 被引用回数:12 パーセンタイル:84.09(Physics, Multidisciplinary)

$$sim$$230MeV/nucleonでの$$^{52}$$Caからの中性子ノックアウト反応が$$gamma$$線分光と行われ、$$1f_{7/2}$$$$2p_{3/2}$$軌道からの中性子ノックアウト反応の運動量分布が測定された。断面積は$$N=32$$の閉殻と整合し、Ca同位体での$$N=28$$$$N=34$$閉殻と同程度に強い閉殻であることが確認された。運動量分布の分析から$$1_{f7/2}$$$$2p_{3/2}$$軌道の平均二乗根半径の差は0.61(23)fmと決定され、これはmodified-shell-modelによる予言の0.7fmと整合した。これは、中性子過剰なCa同位体での$$2p_{3/2}$$軌道半径が大きいことが、中性子数にしたがって線形的に荷電半径が増える意外な現象の原因であることを示唆している。

論文

Real-time observation of charge-spin cooperative dynamics driven by a nonequilibrium phonon environment

黒山 和幸*; 松尾 貞茂*; 村本 丈*; 藪中 俊介; Velentin, S. R.*; Ludwig, A.*; Wieck, A. D.*; 都倉 康弘*; 樽茶 清悟*

Physical Review Letters, 129(9), p.095901_1 - 095901_6, 2022/08

 被引用回数:2 パーセンタイル:34.68(Physics, Multidisciplinary)

We report on experimental observations of charge-spin cooperative dynamics of two-electron states in a GaAs double quantum dot located in a nonequilibrium phonon environment. When the phonon energy exceeds the lowest excitation energy in the quantum dot, the spin-flip rate of a single electron strongly enhances. In addition, originated from the spatial gradient of phonon density between the dots, the parallel spin states become more probable than the antiparallel ones. These results indicate that spin is essential for further demonstrations of single-electron thermodynamic systems driven by phonons, which will greatly contribute to understanding of the fundamental physics of thermoelectric devices.

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