Ibaraki University's
Graduate School of Science and Engineering (Science)
Department of Science (Physics Course)


IGA Fumitoshi

Other affiliation / position

  1. Frontier Research Center for Applied Atomic Sciences Vice president
  2. Professor
  3. Institute for Liberal Arts Education Department of Arts and Sciences 兼務教員


  1. 日本学術振興会 特別研究員DC 1987/04/01-1989/03/31
  2. 通商産業省(現経済産業省)工業技術院電子技術総合研究所 研究員 1989/04/01-1994/03/31
  3. 通商産業省 工業技術院電子技術総合研究所(現産業技術総合研究所) 主任研究員 1994/04/01-1996/03/31
  4. 通商産業省工業技術院に出向 超伝導開発プロジェクト担当 1995/04/01-1995/09/30
  5. 電子技術総合研究所 帰任 1995/10/01-1996/03/31
  6. 広島大学理学部物性学科 助教授 1996/04/01-1998/03/31
  7. 広島大学大学院先端物質科学研究科助教授 1998/04/01-2007/03/31
  8. 広島大学大学院先端物質科学研究科准教授 2007/04/01-2011/03/31
  9. 茨城大学理学部物理コース 理工学研究科理学専攻 教授 2011/04/01-Present
  10. フロンティア応用原子科学研究センター 副センター長 2015/04/01-Present
  11. 大学院理工学研究科 量子線科学専攻 物質量子科学コース 教授 2016/04/01-Present

Academic background

  1. Tohoku University Faculty of Science Department of Physics 1982/03 Graduated
  2. Tohoku University Graduate School, Division of Natural Science 物理学第2専攻 Doctor later 1989/03 Completed

Academic degrees

  1. 理学博士 Tohoku University 1989/03

Current state of research and teaching activities

・近藤半導体の超強磁場(100 T),超高圧下(100 GPa超)の物性研究で金属非金属転移を探索
・超高圧下合成(20 GPa超)で新規のホウ化物、酸化物を開発

Research Areas

  1. Physical Properties I
  2. Physical Properties II

Research keywords

  1. 磁性、強相関電子系、物質開発、超高圧合成

Subject of research

  1. トポロジカル近藤絶縁体の基礎研究(YbB_12, SmB_6) 強相関半導体の一種、近藤半導体が実はトポロジカル絶縁体(表面が金属,バルクは絶縁体に自然となる)であることを最近明らかにした。光電子分光により,表面の電子状態や,バルクの電子構造を観測した. 2015/04/01-Present

Proposed theme of joint or funded research

  1. 最大20GPaの高圧環境を利用した新素材開発 Wish to undertake joint research with industry and other organizations including private sector. Commisioned research,Joint research 産学連携他広く門戸を開けて,高圧環境を駆使した物質作成の場を提供する.
  2. 光集中加熱法による単結晶育成 Wish to undertake joint research with industry and other organizations including private sector. Commisioned research,Joint research 最高2800℃の高温空間を作れるクセノン四楕円炉を1997年に開発した.この装置は後に世界的に広がったが,その1号機は茨城大で原液で活躍している.この装置により,希土類ホウ化物の純良単結晶を育成しているが、いろんな金属化合物の結晶育成にも応用できることは実証済みである.アイデアを持ち込んでくれれば,その純良単結晶作りにトライしたい.


  1. 希土類ホウ化物の高圧合成 伊賀文俊 日本高圧力学会「高圧力の科学と技術」26巻 no.3 日本高圧力学会 2016/09/01 In this article, recent advances in the fundamental and applied high-pressure synthesis of rare-earth borides, especially RB_12, were reviewed. High pressure equipment using the Walker module has been first introduced to Ibaraki university. It seems very covenant for primary users of high-pressure synthesis to use the equipment. We expect novel materials which have exotic physical properties.
  2. 希土類ホウ化物の高圧合成 伊賀文俊 高圧力の科学と技術,vol.26, No.3 日本高圧力学会 2016/09/01
  3. 「物理データ事典」第4章 量子物性 18. 磁性 「18.3. 近藤物質」 Fumitoshi Iga 日本物理学会編集、朝倉書店 2006 強相関化合物の近藤物質の近藤温度の他、特徴的な温度をまとめた


  1. Research paper (scientific journal) Joint Evidence for in-gap surface states on the single-phase SmB6(001) surface Toshio Miyamachi, Shigemasa Suga, Martin Ellguth, Christian Tusche, Claus Schneider, Fumitoshi Iga, and Fumio Komori Scientific Reports Nature 7, 12837(1)-12837(7) 2017/10/09 10.1038/s41598-017-12887-2 Structural and electronic properties of the SmB6(001) single-crystal surface prepared by Ar+ ion sputtering and controlled annealing are investigated by scanning tunneling microscopy. In contrast to the cases of cleaved surfaces, we observe a single phase lattice on the entire surface at an optimized annealing temperature. The surface is identified as surface with a non-reconstructed p(1 × 1) Sm-terminated on the basis of spectroscopic measurements. On a structurally uniform surface, the emergence of the in-gap state, a robust surface state against structural variation, is further confirmed inside a Kondo hybridization gap at 4.4 K by temperature and atomically-resolved spatial dependences of the differential conductance spectrum near the Fermi energy.
  2. Research paper (scientific journal) Joint Hard x-ray photoemission study of Yb1−xZrxB12 :the effects of electron doping on the Kondo insulator YbB12 A Rousuli1, H Sato2, F Iga3, K Hayashi4, K Ishii4, T Wada4,T Nagasaki1, K Mimura5, H Anzai5, K Ichiki5, S Ueda6,7A Kondo8, K Kindo8, T Takabatake9,10, K Shimada, H Namatame2, M Taniguchi2 Journal of Physics: Condensed Matter 29, 265601(1)-265601(7) 2017/05/26 10.1088/1361-648X/aa6f70 We have carried out hard x-ray photoemission spectroscopy (HAXPES) of Yb1−xZrxB12 (0 ≤ x ≤ 0.875) to study the effects of electron doping on the Kondo insulator YbB12. The Yb valences of Yb1−xZrxB12 at 300 K estimated from the Yb 3d HAXPES spectra decreased after substituting Yb with Zr from 2.93 for YbB12 to 2.83 for Yb0.125Zr0.875B12. A temperature dependent valence decrease was found upon cooling for all doping concentrations. We found peak shifts of the B 1s and Zr 3d5/2, and Yb3+ 4f spectra toward the deeper binding-energy with increasing Zr concentration, which indicates a shift of the Fermi level to the higher energy and that of the Yb 4f hole level close to the Fermi level, respectively, due to electron doping. These results qualitatively show the enhanced hybridization between the Yb 4f and conduction-band states with Zr substitution, consistent with magnetic susceptibility measurements.
  3. Research paper (scientific journal) Joint Magnetization process of the Kondo Insulator YbB12 in ultrahigh magnetic field Taku. T. Terashima, Akihiko Ikeda, Tasuhiro H. Matsuda, Akihiro Kondo, Koichi Kindo, Fumitoshi Iga Journal of the Physical Society of Japan 日本物理学会 86, 54710 2017/04/24 10.7566/JPSJ.86.054710 The magnetization process of the Kondo insulator YbB12 has been unveiled in ultrahigh magnetic fields of up to 120 T at 4.2 K. We have found a novel metamagnetic transition at Bc2 = 102 T in addition to the previously known transition at Bc1 = 55 T. It has also been observed that the magnetization tends to saturate at around 112 T. Within the rigid band model, the two-energy-gap structure in the density of states (DOS) explains the successive two-step metamagnetism as a result of the Zeeman effect of the DOS. The metamagnetic transition at Bc1 occurs along with an insulator–metal transition and the field-induced phase is expected to be a heavy fermion metallic state. The Kondo effect can weaken at the second transition of Bc2, as theoretically found in the successive two-metamagnetic-transition process in the Kondo semimetal CeNiSn.
  4. Research paper (scientific journal) Joint Temperature dependence of Yb valence in the sub-surface of YbB12(001) Kenta Hagiwara,1 Yusuke Takeno,1 Yoshiyuki Ohtsubo,1, 2 Ryu Yukawa,3 Masaki Kobayashi,3 Koji Horiba,3 Hiroshi Kumigashira,3 Julien Rault,4 Patrick Le Fèvre,4 François Bertran,4 Amina Taleb-Ibrahimi,4, 5 Fumitoshi Iga,6 Shin-ichi Kimura1, 2 IOP Conf. Series: Journal of Physics: Conf. Series IOP 807, 12003 2017/04/12 10.1088/1742-6596/807/1/012003 The typical Kondo insulator, YbB12, is a candidate of topological Kondo insulators. To clarify the surface electronic structure of not only bulk but also surface by photoelectron measurements, we developed a method to obtain a clean surface of YbB12(001) by annealing at 1650 K in an ultra-high vacuum. By surface-sensitive photoelectron measurements, it was known that the surface consists of only B atoms without Yb. In the sub-surface region, Yb atoms exist and the temperature dependence of the valence agrees with those of previous HAXPES results. Here we report the cleaning method to obtain well-defined YbB12(001) surfaces and the temperature-dependent Yb valence obtained from Yb 3d core-level and valence photoelectron spectra.
  5. Research paper (scientific journal) Joint Different valence states of Tm in YB6 and YbB6 H. Satoa, , , H. Nagatab, F. Igac, Y. Osanaid, A. Rousulib, K. Mimurae, H. Anzaie, K. Ichikie, S. Uedaf, g, T. Takabatakeh, i, A. Kondoj, K. Kindoj, K. Shimadaa, H. Namatamea, M. Taniguchia Journal of Electron Spectroscopy and Related Phenomena 2017/03/08 10.1016/j.elspec.2017.03.006 We have investigated the electronic structures of Y1-xTmxB6 (x = 0, 0.25) and Yb1-xTmxB6 (x = 0, 0.2) by means of hard x-ray photoemission spectroscopy (HAXPES) at h ν = 5.95 keV. The Tm 3d HAXPES revealed that the valence of Tm in YB6 is ∼2.6 at 300 K and ∼2.5 at 20 K, indicating strong valence fluctuation. In contrast, Tm in YbB6 is almost trivalent independent of temperature. Yb in YbB6 is almost divalent and the Yb2+ state is stabilized by the Tm doping.

Research presentations

  1. Oral presentation(invited, special) Concluding remarks 茨城大学量子線科学国際シンポジウム 2017/12/10
  2. Oral presentation(invited, special) 近藤絶縁体YbB12の熱伝導率 日本物理学会 2017年秋季大会 2017/09/23
  3. Oral presentation(invited, special) 近藤絶縁体YbB12における量子振動の観測 日本物理学会 2017年秋季大会 2017/09/23
  4. Poster presentation Ce化合物/超伝導界面の点接合分光実験 日本物理学会 2017年秋季大会 2017/09/22
  5. Poster presentation 近藤絶縁体YbB12のYbサイト2価イオン置換効果 日本物理学会 2017年秋季大会 2017/09/22

Alloted class

  1. 情報処理概論(情報リテラシー)
  2. 磁性物理学1
  3. 磁性物理学2
  4. 磁性物理学1(理学専攻)
  5. 磁性物理学2(理学専攻)

Memberships of academic societies

  1. 日本高圧力学会 2001/04-Present
  2. 日本磁気学会 1989/04-Present
  3. 日本物理学会 1982/04-Present

Committee Career

  1. 量子線科学専攻 国際シンポジウム実行委員会実行委員長 2017/08/01-2017/12/31
  2. 日本物理学会 日本物理学会第73~74期代議員 2017/03/31-2019/03/31
  3. 物性グループ 物性委員会幹事 2015/10/01-2017/09/30