KEIO RESEARCHERS INFORMATION SYSTEM

Career 【 Display / hide 】

Career 【 Display / hide 】

• 2012.04

  -

  2013.03

  The University of Tokyo, 大学院新領域研究科, 日本学術振興会 特別研究員(PD)

• 2013.04

  -

  2015.06

  理化学研究所, 創発物性科学研究センター, 特別研究員

• 2015.07

  -

  2018.06

  The University of Tokyo, Graduate School of Arts and Sciences, 助教

• 2018.07

  -

  2022.06

  Tohoku university, Institute of Materials Research, Assistant professor

• 2019.10

  -

  2023.03

  科学技術振興機構, さきがけ研究員（兼任）

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Academic Degrees 【 Display / hide 】

Academic Degrees 【 Display / hide 】

• 博士（理学）, Tohoku University, 2012.03

Research Areas 【 Display / hide 】

Research Areas 【 Display / hide 】

• Natural Science / Semiconductors, optical properties of condensed matter and atomic physics

• Natural Science / Magnetism, superconductivity and strongly correlated systems

Research Keywords 【 Display / hide 】

Research Keywords 【 Display / hide 】

• トポロジカル磁気構造

• Nano device

• Acoustics

• マイクロ波光学

• Scanning Microwave Impedance Microscopy

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Papers 【 Display / hide 】

Papers 【 Display / hide 】

• First-principles prediction of chiral-phonon-induced orbital accumulation

  A. Pezo, A. Manchon, Y. Nii, K. Ando, T. Kato

   2026.05

  　View Summary

  Chiral phonons offer a route to transfer angular momentum without relying on magnetic order, but their electronic response in metals remains poorly understood from perspectives beyond spin-based scenarios. Using first-principles calculations, we show that coherent chiral lattice motion generates orbital accumulation and, through spin-orbit coupling, a smaller accompanying spin accumulation. Our approach evaluates orbital and spin expectation values directly from strain perturbed ab initio Hamiltonians in the long-wavelength limit, where the phonon perturbation is represented by symmetry adapted circular lattice distortions. We show that the response is controlled mainly by orbital character, near-degeneracies, and electron-phonon coupling, rather than by spin-orbit coupling alone. These results identify light transition metals as promising platforms for chiral-phonon-driven orbitronics.

• Direct demonstration of electric chirality control in a helimagnetic YMn$_6$Sn$_6$ by spin-polarized neutron scattering

  Hidetoshi Masuda, Yutaro Yanagisawa, Kazuki Ohishi, Yusuke Nambu, Yoichi Nii, Yoshinori Onose

   2025.12

  　View Summary

  The spiral handedness of magnetic moments, referred to as chirality, gives rise to emergent electromagnetic phenomena in helimagnets. In insulating helimagnets, known as multiferroics, the cycloidal spin structure induces electric polarization by utilizing the inverse Dzyaloshinskii-Moriya mechanism. Spin-polarized neutron diffraction experiments, which directly probe circular spin arrangements, clearly demonstrated that an electric field controlled the chirality in multiferroic helimagnets. On the other hand, it was unclear until recently how the chirality could be controlled in metallic helimagnets where a large electric field cannot be applied, while the chirality control technique in metallic helimagnets should enable the exploration of chirality-dependent spintronic functionalities. Recently, Jiang et al. succeeded in controlling the chirality of a spiral structure by the simultaneous application of a magnetic field and electric current in a metallic helimagnet, utilizing the nonreciprocal electronic transport as an indirect probe of chirality, highlighting the need for a neutron diffraction experiment that directly probes the chirality. Here, we directly demonstrate the chirality control in a metallic helimagnet YMn$_6$Sn$_6$ by means of spin-polarized neutron diffraction, which should give rise to a firm basis for the development of future helimagnetic spintronics.

• Critically-enhanced nonreciprocal electronic transport at magnetic phase boundary in a room temperature helimagnet YMn6Sn6

  Hidetoshi Masuda, Jun-ichiro Ohe, Yoichi Nii, Shojiro Kimura, Yoshinori Onose

  Physical Review Research (American Physical Society (APS))  7 ( 3 ) 033019 2025.07

  Accepted

  　View Summary

  We investigated nonreciprocal electronic transport, a diode effect of electric current flow, in a helimagnet YMn6Sn6. We found that nonreciprocal resistivity, whose sign depends on the handedness of the magnetic spiral (chirality), was drastically enhanced in the vicinity of the helimagnetic transition magnetic field. This critical enhancement was observed in the wide temperature range below the helimagnetic transition temperature 335 K. We comparatively discuss three possible mechanisms of nonreciprocal electronic transport: band asymmetry, current-induced deformation of the magnetic structure, and asymmetric scattering, and suggest the most plausible mechanism is the last one.

  • Access to Document (DOI)

• Current-Induced Sliding Motion in a Helimagnet MnAu2

  Yuta Kimoto, Hidetoshi Masuda, Takeshi Seki, Yoichi Nii, Jun-ichiro Ohe, Yusuke Nambu, Yoshinori Onose

  Physical Review Letters (American Physical Society (APS))  134 ( 5 )  2025.02

  ISSN  0031-9007

  　View Summary

  We found signatures of current-induced sliding motion in helimagnetic MnAu2 thin films. An abrupt change in differential resistivity occurred at a threshold bias current in the helimagnetic state, whereas it was absent in the induced ferromagnetic state. Broadband voltage noise also emerged above the threshold current in the helimagnetic state. Based on the similarity to canonical charge and spin density wave systems, we ascribed the origin of these phenomena to the sliding motion of the helimagnetic structure.
  
  Published by the American Physical Society 2025

  • Access to Document (DOI)

• Band asymmetry-driven nonreciprocal electronic transport in a helimagnetic semimetal a-EuP3

  Alex Hiro Mayo, Darius-Alexandru Deaconu, Hidetoshi Masuda, Yoichi Nii, Hidefumi Takahashi, Rodion Vladimirovich Belosludov, Shintaro Ishiwata, Mohammad Saeed Bahramy, Yoshinori Onose

  Proceedings of the National Academy of Sciences  ( 122(4) ) e2405839122 2025.01

  Research paper (scientific journal), Joint Work, Accepted

  • Access to Document (DOI)

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Reviews, Commentaries, etc. 【 Display / hide 】

Reviews, Commentaries, etc. 【 Display / hide 】

• Magnetoelastic study on the itinerant helimagnet SrFeO₃ and reconsideration of the phase diagram

  厳正輝, 今城周作, 鬼頭俊介, 徳永祐介, 新居陽一, 池田暁彦, 小濱芳允, 金道浩一, 石渡晋太郎, 有馬孝尚, 有馬孝尚

  日本物理学会講演概要集(CD-ROM) 79 ( 1 )  2024

  ISSN  2189-079X

• Observation of phonon dispersion at low temperature phases in FeV₂O₄ using synchrotron X-ray inelastic scattering

  萬條太駿, 鬼頭俊介, 片山尚幸, 中村真一, 勝藤拓郎, 新居陽一, 新居陽一, 有馬孝尚, 有馬孝尚, 長谷川巧, 石川大介, 石川大介, BARON A. Q. R., BARON A. Q. R., 澤博

  日本物理学会講演概要集(CD-ROM) 76 ( 2 )  2021

  ISSN  2189-079X

• Observation of 3d orbital state in spinel oxide FeV₂,O₄ with Fe and V having orbital degree of freedom

  萬條太駿, 鬼頭俊介, 片山尚幸, 野村悠祐, 有田亮太郎, 有田亮太郎, 新居陽一, 新居陽一, 有馬孝尚, 有馬孝尚, 澤博

  日本物理学会講演概要集(CD-ROM) 75 ( 2 )  2020

  ISSN  2189-079X

• Direct observation of valence electron density distribution in AV2O4(A = Fe,Mn) using core differential Fourier synthesis method

  萬條太駿, 鬼頭俊介, 片山尚幸, 新居陽一, 有馬孝尚, 有馬孝尚, 勝藤拓郎, 勝藤拓郎, 澤博

  日本物理学会講演概要集(CD-ROM) 75 ( 1 )  2020

  ISSN  2189-079X

• コア差フーリエ合成解析によるFeV₂O₄の軌道秩序の観測 II

  萬條太駿, 鬼頭俊介, 片山尚幸, 新居陽一, 有馬孝尚, 澤博

  日本物理学会講演概要集(CD-ROM) 74 ( 1 )  2019

  ISSN  2189-079X

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Research Projects of Competitive Funds, etc. 【 Display / hide 】

Research Projects of Competitive Funds, etc. 【 Display / hide 】

• 対称性の破れた絶縁体における新しい変位電流応答の開拓

  2024.06

  -

  2026.03

  挑戦的研究(萌芽), Research grant, Principal investigator

• 対称性の破れた絶縁体における新しい変位電流応答の開拓

  2024.06

  -

  2026.03

  挑戦的研究（萌芽）, Principal investigator

• Gigahertz Phononic Devices with Topological Functionalities

  2024.04

  -

  2027.03

  基盤研究(B), Principal investigator

• 超低損失なGHzトポロジカルフォノニックデバイスの創出

  2024.04

  -

  2027.03

  日本学術振興会 科学研究費助成事業 基盤研究(B), Principal investigator

• 先端計測による強相関フォノニクスと熱機能の開拓

  2023.04

  -

  2030.03

  創発的研究支援事業, Principal investigator

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Awards 【 Display / hide 】

Awards 【 Display / hide 】

• 文部科学大臣表彰 若手科学者賞

  2024.04

• 第140回金研講演会 優秀ポスター賞

  新居陽一, 廣金優二, 是常隆, 石川大介, Alfred Q. R. Baron, 小野瀬佳文, 2021.05, 東北大学金属材料研究所, キラル磁性体MnSi のフォノン分散に及ぼす対称性の破れの効果

• Best poster awards in Summit of Materials Science conference

  Yoichi Nii, 2018.10, Institute for Materials Research, Tohoku university

• JPSJ Editor's Choice, Microwave Magnetochiral Effect in the Non-centrosymmetric Magnet CuB2O4

  Yoichi Nii, Ryo Sasaki, Yusuke Iguchi, Yoshinori Onose, 2017.01, Journal of the Physical Society of Japan

Courses Taught 【 Display / hide 】

Courses Taught 【 Display / hide 】

• INDEPENDENT STUDY ON FUNDAMENTAL SCIENCE AND TECHNOLOGY

  2026

• SOLID STATE PHYSICS 1

  2026

• APPLIED PHYSICS AND PHYSICO-INFORMATIC PRACTICAL RESEARCH C

  2026

• PRESENTATION TECHNIQUE

  2026

• GRADUATE RESEARCH ON MATHEMATICAL AND PHYSICAL SCIENCES 2

  2026

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Memberships in Academic Societies 【 Display / hide 】

Memberships in Academic Societies 【 Display / hide 】

• 応用物理学会, 

  2022

  -

  Present

• 日本物理学会, 

  2009

  -

  Present