Research activity information

• Raman Characterization of Two-Dimensional Quasiperiodic Antiferromagnets on Various Lattices: Spin–Orbit Mechanism
  Takashi Inoue; Shoji Yamamoto
  Journal of the Physical Society of Japan, 95, 6, Physical Society of Japan, 15 Jun. 2026, [Peer-reviewed]
  Scientific journal
• Superconfined Antiferromagnons on the Two-Dimensional Penrose Lattice
  Takashi Inoue; Shoji Yamamoto
  Crystals, 16, 6, 370, 370, MDPI AG, 01 Jun. 2026, [Peer-reviewed]
  English, Scientific journal, We find novel confined states in the spin-S nearest-neighbor antiferromagnetic Heisenberg model on the two-dimensional Penrose lattice. Linear spin waves have massively degenerate eigenstates strictly confined to tricoordinated sites. They contrast with the well-known itinerant analogs in the tight-binding model, where electrons are confined but extended to both tricoordinated and pentacoordinated sites. It is the site potentials in the spin-wave Hamiltonian, originating from Coulomb interactions between electrons, that confine spin waves to minimally coordinated sites only. Confined states in the tight-binding Hamiltonian consist of six types of building blocks, whereas those in the spin-wave Hamiltonian consist of only four of them. Confined spin waves are robust against 1/S corrections. Emergent O(S0) interactions further confine—superconfine—spin waves into two separate groups within tricoordinated sites.
• Magnon Confinement on the Two-Dimensional Penrose Lattice: Perpendicular-Space Analysis of the Dynamic Structure Factor
  Shoji Yamamoto; Takashi Inoue
  Crystals, 14, 8, 702, 702, MDPI AG, 01 Aug. 2024, [Peer-reviewed]
  English, Scientific journal, Employing the spin-wave formalism within and beyond the harmonic-oscillator approx-imation, we study the dynamic structure factors of spin-12 nearest-neighbor quantum Heisenberg antiferromagnets on two-dimensional quasiperiodic lattices with particular emphasis on a mag-netic analog to the well-known confined states of a hopping Hamiltonian for independent electrons on a two-dimensional Penrose lattice. We present comprehensive calculations on the C5v Penrose tiling in comparison with the C8v Ammann–Beenker tiling, revealing their decagonal and octagonal antiferromagnetic microstructures. Their dynamic spin structure factors both exhibit linear soft modes emergent at magnetic Bragg wavevectors and have nearly or fairly flat scattering bands, signifying magnetic excitations localized in some way, at several different energies in a self-similar manner. In particular, the lowest-lying highly flat mode is distinctive of the Penrose lattice, which is mediated by its unique antiferromagnons confined within tricoordinated sites only, unlike their itinerant electron counterparts involving pentacoordinated, as well as tricoordinated, sites. Bringing harmonic antiferromagnons into higher-order quantum interaction splits, the lowest-lying nearly flat scattering band in two, each mediated by further confined antiferromagnons, which is fully demonstrated and throughly visualized in the perpendicular as well as real spaces. We disclose superconfined antiferromagnons on the two-dimensional Penrose lattice.
• Polarized Raman Response of Two-Dimensional Quasiperiodic Antiferromagnets: Configuration-Interaction versus Green’s Function Approaches
  Takashi Inoue; Shoji Yamamoto
  Journal of the Physical Society of Japan, 91, 5, Physical Society of Japan, 15 May 2022, [Peer-reviewed]
  English, Scientific journal
• Optical Observation of Quasiperiodic Heisenberg Antiferromagnets in Two Dimensions
  Takashi Inoue; Shoji Yamamoto
  physica status solidi (b), Nov. 2020, [Peer-reviewed]
  Scientific journal

• Perpendicular-space analysis of one-magnon-mediated Raman scattering in quasiperiodic antiferromagnets
  井上天; 山本昌司, 日本物理学会講演概要集(CD-ROM), 76, 1, 2021
• Raman spectra of ring-exchange antiferromagnets on the Penrose lattice
  Inoue Takashi; Yamamoto Shoji, Meeting Abstracts of the Physical Society of Japan, 75.1, 1500, 1500, 2020
  The Physical Society of Japan, Japanese
• Magnetic Raman scattering beyond the Loudon-Fleury mechanism in the Heisenberg antiferromagnet on the Penrose lattice
  Inoue Takashi; Yamamoto Shoji, Meeting Abstracts of the Physical Society of Japan, 74.1, 1696, 1696, 2019
  The Physical Society of Japan, Japanese
• One- and two-magnon-mediated Raman scattering in Penrose-lattice antiferromagnets
  Inoue Takashi; Yamamoto Shoji, Meeting Abstracts of the Physical Society of Japan, 74.2, 1342, 1342, 2019
  The Physical Society of Japan, Japanese
• Magnetic Raman scattering in two-dimensional quasiperiodic Heisenberg antiferromagnets
  Inoue Takashi; Yamamoto Shoji, Meeting Abstracts of the Physical Society of Japan, 73.2, 1149, 1149, 2018
  The Physical Society of Japan, Japanese
• 21aBD-13 Theory of magnetic Raman scattering in antiferromagnetic spin tubes
  INOUE Takashi; YAMAMOTO Shoji, Meeting Abstracts of the Physical Society of Japan, 71.1, 1231, 2016
  The Physical Society of Japan, Japanese
• 16aCQ-7 Schwinger-boson representation of anisotropic quantum spin models
  INOUE Takashi; YAMAMOTO Shoji, Meeting Abstracts of the Physical Society of Japan, 70.2, 2533, 2015
  The Physical Society of Japan, Japanese

• Spin-orbit-coupling-driven Raman scattering in two-dimensional quasiperiodic and periodic XXZ antiferromagnets
  Takashi Inoue; Shoji Yamamoto
  日本物理学会 第80回年次大会, 17 Sep. 2025, Japanese, Oral presentation
  15 Sep. 2025 - 19 Sep. 2025
• Optical observations of two-dimensional quasiperiodic antiferromagnets
  井上天
  新学術領域「ハイパーマテリアル：補空間が創る新物質科学」第29回ハイパーマテリアル・セミナー, Jul. 2023, Japanese, Public discourse
  [Invited]
• Magnon localization in the two-dimensional Penrose antiferromagnet: Perpendicular-space analysis of the dynamic structure factor
  Takashi Inoue; Shoji Yamamoto
  日本物理学会 2023年春季大会, Mar. 2023, Oral presentation
• Perpendicular-space analysis of one-magnon-mediated Raman scattering in quasiperiodic antiferromagnets
  Takashi Inoue; Shoji Yamamoto
  日本物理学会 第76回年次大会, Mar. 2021, Japanese, Oral presentation
• Optical observation of quasiperiodic Heisenberg antiferromagnets in two dimensions
  Takashi Inoue; Shoji Yamamoto
  14th International Conference on the Structure of Non-Crystalline Materials (NCM14), Nov. 2019, English, Oral presentation
• One- and two-magnon-mediated Raman scattering in Penrose-lattice antiferromagnets
  Takashi Inoue; Shoji Yamamoto
  日本物理学会 2019年秋季大会, Sep. 2019, Japanese, Oral presentation
• Spin-chirality-driven Raman scattering in Penrose-lattice Heisenberg antiferromagnets
  Takashi Inoue; Shoji Yamamoto
  Interdisciplinary Symposium for Quasicrystals and Strongly Correlated Electron Systems (QSC2019), Jun. 2019, English, Poster presentation
• Penrose格子Heisenberg反強磁性体の超Loudon-Fleury磁気Raman散乱理論
  井上天; 山本昌司
  日本物理学会 第74回年次大会, Mar. 2019, Japanese, Oral presentation
• 2次元準周期Heisenberg反強磁性体の磁気Raman散乱
  井上天; 山本昌司
  日本物理学会 2018年秋季大会, Sep. 2018, Oral presentation
• 反強磁性スピン・チューブの磁気Raman散乱理論
  井上天; 山本昌司
  日本物理学会 第71回年次大会, Mar. 2016, Oral presentation
• 異方的量子スピン模型のSchwingerボソン解析
  井上天; 山本昌司
  日本物理学会 2015年秋季大会, Sep. 2015, Oral presentation

• Jun. 2015 - Present
  The Physical Society of Japan