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Rajeev, H. S.*; Hu, X.*; Chen, W.-L.*; Zhang, D.*; Chen, T.*; 古府 麻衣子*; 梶本 亮一; 中村 充孝; Chen, A. Z.*; Johnson, G. C.*; et al.
Journal of the Physical Society of Japan, 94(3), p.034602_1 - 034602_14, 2025/03
Two-dimensional hybrid organic-inorganic perovskites (HOIPs) have emerged as promising materials for light-emitting diode applications. In this study, by using time-of-flight neutron spectroscopy we identified and quantitatively separated the lattice vibrational and molecular rotational dynamics of two perovskites, butylammonium lead iodide (BA)
PbI
and phenethyl-ammonium lead iodide (PEA)PbI. By examining the corresponding temperature dependence, we found that the lattice vibrations, as evidenced by neutron spectra, are consistent with the lattice dynamics obtained from Raman scattering. We revealed that the rotational dynamics of organic molecules in these materials tend to suppress their photoluminescence quantum yield (PLQY) while the vibrational dynamics did not show predominant correlations with the same. Additionally, we observed photoluminescence emission peak splitting for both systems, which becomes prominent above certain critical temperatures where the suppression of PLQY begins. This study suggests that the rotational motions of polarized molecules may lead to a reduction in exciton binding energy or the breaking of degeneracy in exciton binding energy levels, enhancing non-radiative recombination rates, and consequently reducing photoluminescence yield. These findings offer a deeper understanding of fundamental interactions in 2D HOIPs and could guide the design of more efficient light-emitting materials for advanced technological applications.
前田 瑞穂*; 松田 達磨*; 芳賀 芳範; 白崎 謙次*; 木村 憲彰*
Journal of the Physical Society of Japan, 94(2), p.024707_1 - 024707_6, 2025/01
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)We investigate the pressure dependence of the magnetoresistivity and Hall resistivity for an itinerant-electron metamagnet UCoAl. The first-order metamagnetic transition point varies as a function of hydrostatic pressure and terminates at the critical pressure 2.0 GPa. The electronic system, however, does not show criticality at this pressure but extends to higher pressures, unlike the usual quantum critical behavior.
永井 佑紀; 富谷 昭夫*
Journal of the Physical Society of Japan, 93(11), p.114007_1 - 114007_8, 2024/11
被引用回数：1 パーセンタイル：0.00(Physics, Multidisciplinary)生成AIにおける基幹技術であるTransformerを用いた新しい自己学習モンテカルロ法を提案した。本研究では、文章における距離の離れた単語の関連性を推測することができるTransformerのAttention機構を用いることにより、電子系の相転移で重要となる長距離相関を効率よく取り込める有効模型を構築した。さらに、スピン回転、空間並進など系が満たすべき対称性をネットワークに取り込むことにより、パラメータ数を劇的に減らすことに成功した。また、レイヤー数を増やすにつれてlossが減っていくというスケーリング則を見出した。
in the early-stage sample of spin-triplet superconductor UTe
北川 俊作*; 徳永 陽; 酒井 宏典; 神戸 振作; 他11名*
Journal of the Physical Society of Japan, 93(12), p.123701_1 - 123701_5, 2024/11
被引用回数：1 パーセンタイル：58.36(Physics, Multidisciplinary)We report the re-measurement of the 
-axis spin susceptibility component in an early-stage sample of the spin-triplet superconductor UTe with the transition temperature of 
= 1.6 K. Using Knight-shift measurements along the 
axis and at a 10-degree tilt from the axis towards the axis, we accurately determined the -axis component without directly measuring the -axis Knight shift. The experiment reveals that the previously reported absence of the reduction in Knight shift is attributed to the missing of signal from the superconducting region and to the detection of residual signals from the non-superconducting region instead.
中島 多朗*; 齋藤 開*; 小林 尚暉*; 川崎 卓郎; 中村 龍也; 古川 はづき*; 浅井 晋一郎*; 益田 隆嗣*
Journal of the Physical Society of Japan, 93(9), p.091002_1 - 091002_5, 2024/09
被引用回数：2 パーセンタイル：58.36(Physics, Multidisciplinary)Neutron scattering is a powerful tool to study magnetic structures and cross-correlated phenomena originated from symmetry of the magnetic structures in matter. Among a number of neutron scattering techniques, polarized neutron scattering is quite sensitive to the orientations of the magnetic moments, which are essential to understand microscopic mechanisms of the spin-driven emergent phenomena. Here, we present POlarized Neutron Triple-Axis spectrometer PONTA in the Japan Research Reactor 3 (JRR-3), and show the present capabilities of polarized and unpolarized neutron scattering by introducing recent results from the instrument.
小沢 耀弘*; 荒木 康史; 野村 健太郎*
Journal of the Physical Society of Japan, 93(9), p.094704_1 - 094704_9, 2024/09
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)磁性ワイル半金属における磁化の変調は、運動量空間におけるワイル点位置のシフトを引き起こし、ワイルフェルミオンに対して実効的なカイラリティ依存のゲージ場として働く。本研究では、完全スピン偏極したワイル強磁性体Co
SnSにおいて、このような磁化誘起カイラルゲージ場の効果を取り扱う。磁化と結合した積層カゴメ格子上で定義したCoSnSの強束縛模型を用いて、運動量空間におけるワイル点の位置(カイラルゲージ場に相当)の磁化方向依存性を計算した。これを用いて、磁壁構造が存在する場合に、カイラルゲージ場の空間構造から生じるカイラル磁場を評価した。その結果磁壁存在下では、ワイルフェルミオンに対してランダウ量子化を強く引き起こすほどの、数百テスラという巨大なカイラル磁場が生じることが導出された。このような巨大カイラル磁場は、従来の磁性体スピントロニクスにおけるスピン起電力に相当する、磁壁の運動による電荷ポンピングを誘起することも予想される。
秋葉 宙*; 大政 義典*; 古府 麻衣子*; Zhang, M.*; 佐藤 駿*; 山室 修*
Journal of the Physical Society of Japan, 93(9), p.091010_1 - 091010_6, 2024/09
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)AGNES is a direct geometry chopper-type time-of-flight neutron spectrometer installed at the cold neutron guide (C3-1-1) of JRR-3 (Tokai, Japan). This instrument is well-suited for studies on low-energy excitations of powdered and amorphous samples, and quasi-elastic scattering with an energy resolution of 120 
eV (standard mode) or 50 eV (high-resolution mode). During the long shutdown period of JRR-3 due to the Great East Japan Earthquake in 2011, AGNES was significantly improved through the installation of supermirror-coated neutron guide tubes and collimator, installation of a new-type top-loading cryo-furnace, and renewal of data acquisition electronics and software. As a result, the neutron intensity has increased by 7.7 times in the standard mode and by 3.2 times in the high-resolution mode. These enhancements facilitate experiments with small amounts of samples, and under special environments, which have previously been challenging.
Si今 布咲子*; 田端 千紘; 齋藤 開*; 中島 多朗*; 日高 宏之*; 柳澤 達也*; 網塚 浩*
Journal of the Physical Society of Japan, 93(4), p.044701_1 - 044701_11, 2024/04
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)We investigated the magnetic structure of the antiferromagnetic (AFM) ordered state (
34 K) in tetragonal UPtSi using polarized and unpolarized neutron diffraction. Previous neutron scattering studies reported that this system possesses a simple AFM structure with a propagation vector, Q= 0, and the ordered magnetic moments aligned along the c-axis. By contrast, our latest resonant X-ray scattering (RXS) experiments have revealed that the magnetic structure is modulated by the charge-density-wave (CDW) order, which emerges in one of the two Pt atomic layers in the unit cell below 320 K. The modulation is characterized by a transverse wave in the c-plane, with the propagation vector of the CDW order, q
= (0.42, 0, 0). In this study using neutron scattering, we observed that the superlattice reflections specified by q develop below , in addition to the magnetic reflections with Q= 0, thereby further confirming the presence of modulation in the AFM structure of this system. From detailed analyses, we revealed that the amplitude of the transverse-wave magnetic modulation is 0.72(2)
/U, which is quantitative information that can not be obtained through RXS experiments. This implies that the CDW drives the ordered magnetic moments to be tilted up to 20
in the AFM state. The observations strongly suggest that the magnetism of UPtSi is heavily influenced by the hybridization effects between the 
electrons of U and the 5d electrons of Pt.
竹内 徹也*; 本多 史憲*; 青木 大*; 芳賀 芳範; 木田 孝則*; 鳴海 康雄*; 萩原 政幸*; 金道 浩一*; 軽部 皓介*; 播磨 尚朝*; et al.
Journal of the Physical Society of Japan, 93(4), p.044708_1 - 044708_10, 2024/04
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)Electrical and magnetic properties of divalent europium antiferromagnet EuTe are studied on single crystals grown from Te-flux method. Antiferromagnetism occurs at 11 K with an insulating ground state. Application of magnetic field induces a sudden resistance drop leading to a phase transition to metallic state. Energy band calculations reveal the appearance of a Fermi surface pocket with Te-5p character induced by the polarized Eu moments.
伊藤 孝; 門野 良典*
Journal of the Physical Society of Japan, 93(4), p.044602_1 - 044602_7, 2024/04
被引用回数：2 パーセンタイル：76.47(Physics, Multidisciplinary)We propose a model to describe the fluctuations in the internal magnetic field due to ion dynamics observed in muon spin relaxation (SR) by an Edwards-Anderson-type autocorrelation function that separates the quasi-static and dynamic components of the correlation by the parameter 
(where 
). Our Monte Carlo simulations for this model showed that the time evolution of muon spin polarization deviates significantly from the Kubo-Toyabe function. To further validate the model, the results of simulations were compared with the SR spectra observed in a hybrid organic-inorganic perovskite FAPbI
[with FA referring to HC(NH)], where local field fluctuations associated with the rotational motion of FA molecules and quasi-static fields from the PbI lattice are presumed to coexist. The least-squares curve fitting showed reasonable agreement with the model with 
, and the fluctuation frequency of the dynamical component was obtained. This result opens the door to the possibility of experimentally distinguishing fluctuations due to the dynamics of ions around muons from those due to the self-diffusion of muons. On the other hand, it suggests the need to carefully consider the spin relaxation function when applying SR to the issue of ion dynamics.
久保 勝規
Journal of the Physical Society of Japan, 93(2), p.024708_1 - 024708_8, 2024/02
被引用回数：4 パーセンタイル：84.87(Physics, Multidisciplinary)We investigate the Hubbard model with the Rashba spin-orbit coupling on a square lattice. The Rashba spin-orbit coupling generates two-dimensional Weyl points in the band dispersion. In a system with edges along [11] direction, zero-energy edge states appear, while no edge state exists for a system with edges along an axis direction. The zero-energy edge states with a certain momentum along the edges are predominantly in the up-spin state on the right edge, while they are predominantly in the down-spin state on the left edge. Thus, the zero-energy edge states are helical. By using a variational Monte Carlo method for finite Coulomb interaction cases, we find that the Weyl points can move toward the Fermi level by the correlation effects. We also investigate the magnetism of the model by the Hartree-Fock approximation and discuss weak magnetic order in the weak-coupling region.
S-nuclear magnetic resonance measurements吉田 章吾*; 芳賀 芳範; 藤井 拓斗*; 中井 祐介*; 水戸 毅*; 他8名*
Journal of the Physical Society of Japan, 93(1), p.013702_1 - 013702_5, 2024/01
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)In Kondo insulators, a small energy gap evolves only at low temperatures. In this study, S-nuclear magnetic resonance measurements under high pressures are performed to clarify the electronic structure of SmS. The spin-lattice relaxation time, consisting of multiple components, was analyzed based on a periodic Anderson model with Bayesian inference, leading to a peculiar small gap state arising from strong hybridization.
Mo for production of medical 
Tc by Mo(
)Tc橋本 慎太郎; 永井 泰樹*
Journal of the Physical Society of Japan, 92(12), p.124202_1 - 124202_11, 2023/12
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)
Moの娘核種であるテクネチウム99m(Tc)は6時間の半減期で
線を出す放射性核種(RI)であり、SPECTなどの診断用RIとして世界中で用いられている。親核種のMoは原子炉で生成されているが、原子炉施設の老朽化等で安定供給が危ぶまれており、医療用加速器で濃縮Mo試料に陽子を照射し、Mo()
Tc反応を通じて生成する方法が提案されている。しかし、試料に微量に含まれるMo以外のMo同位体から、Tc以外のTcが生成される問題がある。そこで本研究では、高純度のTcを生成できるMo組成を調べるために、天然組成のMoの照射実験データに基づいて、全てのTc同位体生成の反応率を決定し、任意の組成をもつMo試料のTc同位体生成量をPHITSを用いて評価する手法を開発した。本手法の有効性を、濃縮Moで生成された各Tcの実測値との比較によって検証するとともに、高純度のTc生成には
Moの各不純物含有量の低減が必須であることを明らかにした。本成果は、照射時間等の施設固有の制約を考慮しながら、高純度のTcを生成する際に必要なMo原料の組成決定に重要な役割を果たす。
and Eu(As
P
)大貫 惇睦*; 軽部 皓介*; 青木 大*; 仲村 愛*; 本間 佳哉*; 松田 達磨*; 芳賀 芳範; 竹内 徹也*
Journal of the Physical Society of Japan, 92(11), p.114703_1 - 114703_12, 2023/11
被引用回数：1 パーセンタイル：26.38(Physics, Multidisciplinary)Single crystal samples of a series of semimetallic magnet Eu(AsP) have successfully grown. By measuring magnetization, Hall resistivity and de Haas-van Alphen oscillations, large anomalous Hall resistivity arising from peculiar magnetic phase diagram was identified.
=1/2 Ising-like antiferromagnetic chain CsCoCl in longitudinal magnetic fields studied by high-field ESR measurements木村 尚次郎*; 大西 弘明; 奥西 巧一*; 赤木 暢*; 鳴海 康雄*; 萩原 政幸*; 金道 浩一*; 菊池 彦光*
Journal of the Physical Society of Japan, 92(9), p.094701_1 - 094701_9, 2023/09
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)High-field electron spin resonance (ESR) measurements were performed on the =1/2 Ising-like antiferromagnetic chain CsCoCl in the frequency range up to 4.4THz and magnetic fields for 
up to 53T. We observed softening of the spinon excitation, which drives the spin chain into the quantum critical state at the critical field 
=33.0T. Above , we observed the string excitation at the wave number 
=
, which is characteristic of the =1/2 spin chain in the quantum critical state in the magnetic fields. We also observed a crossover of the string excitation to the magnon bound state above the saturation fields 
=43.9T upon increasing the magnetic fields. Finally, we discuss how the string excitation and magnon bound state can be excited by the electric dipole transition due to spin quadrupolar resonance.
Shim, S.-I.*; 吉田 数貴; 緒方 一介*
Journal of the Physical Society of Japan, 92(9), p.094201_1 - 094201_8, 2023/09
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)本研究では、歪曲波インパルス近似と平面波インパルス近似の断面積の比を計算し、核子ノックアウト反応とアルファノックアウト反応の断面積に対する吸収効果を系統的に調べた。また、標的原子核の質量数依存性や、ノックアウトされる粒子の一粒子軌道に対する依存性についても調査した。
-Mo
O
revealed by angle-resolved photoelectron spectroscopy and first-principles calculation角田 一樹; 檜垣 聡太*; 佐藤 仁*; 水流 大地*; 宮本 幸治*; 奥田 太一*; 黒岩 芳弘*; 森吉 千佳子*; 高瀬 浩一*; 小口 多美夫*; et al.
Journal of the Physical Society of Japan, 92(8), p.084706_1 - 084706_6, 2023/08
被引用回数：1 パーセンタイル：0.00(Physics, Multidisciplinary)We investigated the electronic structure of -MoO bulk crystal in the whole Brillouin zone at a normal metallic state by utilizing resonant and angle-resolved photoelectron spectroscopies and first-principles calculations. Mo 4
-4
resonant photoelectron experiment revealed that the Mo 4 electrons of MoO
octahedra mainly contributed to the electrical conductivity. We also demonstrated that the free electron-like band dispersions along 
axis, consisting of Mo 4
electrons, do not show clear 
and 
dependences and formed a one-dimensional Fermi surface even at the normal state. The observed low-dimensional and anisotropic band structures are expected to induce exotic physical properties such as quantized bulk Hall effect, charge density wave transitions, and Luttinger liquid behavior.
金子 耕士; 田端 千紘; 萩原 雅人; 山内 宏樹; 久保田 正人; 長壁 豊隆; 大貫 惇睦*
Journal of the Physical Society of Japan, 92(8), p.085001_1 - 085001_2, 2023/08
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)A magnetic order in orthorhombic GdCu was investigated by a single crystal neutron diffraction with thermal neutron. Magnetic peaks were observed at incommensurate positions described by the ordering vector =(
~1~0) with =0.678 at 4~K. This ordering vector is close to the commensurate one with 
=(2/3~1~0) reported earlier, but clearly deviates. The incommensurate nature of the magnetic order in GdCu is further corroborated by the peak shift with temperature below .
針井 一哉*; 埋田 真樹; 有沢 洋希*; 日置 友智*; 佐藤 奈々; 岡安 悟; 家田 淳一
Journal of the Physical Society of Japan, 92(7), p.073701_1 - 073701_4, 2023/07
被引用回数：1 パーセンタイル：26.38(Physics, Multidisciplinary)Magnetic property modification of an easy-plane magnetic insulator caused by an accumulation of nanocolumnar defects along the film normal was investigated by numerical simulations and heavy-ion beam irradiation experiments. Micromagnetic simulations suggest that depending on the density of the nonmagnetic nanocolumnar defects, the microstructure of the fragmented ferromagnetic domains is formed leading to magnetic coercivity enhancement as well as magnetization reduction. To prove this prediction, gold ions with 300 MeV were used for the irradiation to create amorphous nanocolumnar defects in crystalline bismuth-doped lutetium iron garnet (Bi:LuIG) films. As increasing the ion-irradiation dose, the modifications of the saturation magnetization and magnetic coercivity were observed in an uncorrelated manner; the enhancement of magnetic coercivity exhibits a fluence threshold whereas the decrease of saturation magnetization caused by ion-beam damage is monotonic with increasing beam fluence. These behaviors qualitatively agree with the numerical simulations and the models by continuum percolation theory. Because the irradiation effects are controlled by beam fluences, the present method has the potential to be a microstructuring technique for magnetic insulator.
荒木 康史; 家田 淳一
Journal of the Physical Society of Japan, 92(7), p.074705_1 - 074705_9, 2023/06
被引用回数：0 パーセンタイル：0.00(Physics, Multidisciplinary)トポロジカル絶縁体は電子が波数空間でトポロジカル構造を持つことにより、様々な非自明な電磁応答現象を示す。一方で、現在用いられているインダクタ・キャパシタの動作原理は、マクスウェル方程式によって記述される古典電磁気学に基づいている。本研究では絶縁体中のトポロジカル電磁応答が、磁性体中の磁化ダイナミクスと組み合わさることにより、インダクタンス・キャパシタンスを生み出すことを示す。まず、トポロジカル場の理論に基づいて、複素インピーダンスを導出する理論的枠組みを提案する。次にその理論に基づき、接合系のセットアップでインダクタンス・キャパシタンスが発現することを示す。金属磁性体における創発インダクタンスに関する先行研究と比較すると、トポロジカル絶縁体はジュール熱を抑制できるため、素子内での電力損失を大幅に抑制することができる。これによって、トポロジカル電磁応答に起因したインダクタンスは弱電流・高周波数での動作を可能とし、更に電力効率の面でも高い品質係数(Q値)を実現できることを示す。
