Study of high pressure electronic state on iron-oxynictide high-T_C superconductors using as probe for thermoelectric effect

2010 Fiscal Year Final Research Report

• Project/Area Number: 21740260
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Single-year Grants
• Research Field: Condensed matter physics II
• Research Institution: University of the Ryukyus
• Principal Investigator: HEDO Masato 琉球大学, 理学部, 准教授 (00345232)
• Project Period (FY): 2009 – 2010
• Keywords: 高圧力 / ゼーベック効果 / 鉄ヒ素系超伝導体 / 電子状態

Research Abstract

Seebeck coefficient (S/T) of Eu_<0.5>Ca_<0.5>Fe_2As_2 showed sign inversion before appearance of superconducting state (SC) and it was found that state of Fermi surface was notably transmuted just before expression of SC. In the case of EuFe_2As_2 verifying precursor phenomenon of SC, the S/T may change positive with further increasing pressure after negative to zero of S/T and it is expected to present similar behavior of Eu_<0.5>Ca_<0.5>Fe_2As_2. For EuFe_2As_2 and Eu_<0.5>Ca_<0.5>Fe_2As_2, T_2-dependence coefficient A of resistivity was prominently decrease after emergence of SC, it is able to understand that the density of state around Fermi level is distinct decrease above critical pressure P_C in this system.

Research Products

• [Journal Article] Pressure-induced changes in the magnetic and valence state of EuFe_2As_2 (2011)
  • Author(s): K. Matsubayashi, K. Munakata, M. Isobe, N. Katayama, K. Ohgushi, Y. Ueda, N. Kawamura, M. Mizumaki, N. Ishimatsu, M. Hedo, I. Umehara and Y. Uwatoko
  • Journal Title: Physical Review B Volume: 84 Pages: 024502-024506
  • Peer Reviewed
• [Journal Article] Effect of pressure on thermopower and resistivity of EuCo_2P_2 (2010)
  • Author(s): T. Nakama, T. Yoshida, A. Ohno, D. Nakamura, Y. Takaesu, M. Hedo, K. Yagasaki, K. Uchima, T. Fujiwara and T. Shigeoka
  • Journal Title: Journal of Physics: Conference Series Volume: 200 Pages: 032050-032054
  • Peer Reviewed
• [Journal Article] Thermopower measurement under high pressure using "seesaw heating method" (2010)
  • Author(s): M. Hedo, D. Nakamura, Y. Takaesu, T. Fujiwara, K. Uchima, K. Yagasaki and T. Nakama
  • Journal Title: Journal of Physics: Conference Series Volume: 215 Pages: 012186-012184
  • Peer Reviewed
• [Journal Article] Electronic and Magnetic Properties of Rare Earth Compounds RPt_2Ge_2 (R: La-Ho) (2009)
  • Author(s): C. Tonohiro, Y. Nakano, F. Honda, T. Yamada, T. Takeuchi, K. Sugiyama, M. Hagiwara, K. Kindo, T. Matsuda, Y. Haga, M. Hedo, Y. Uwatoko, R. Settai and Y. Onuki
  • Journal Title: Journal of the Physical Society of Japan Volume: 78 Pages: 114706-114709
  • Peer Reviewed
• [Journal Article] Pressure Dependence of Electrical Transport in the Triangular Antiferromagnetic Insulators FeGa_2S_4 and Fe_2Ga_2S_5 (2009)
  • Author(s): T. Tomita, Y. Nambu, S. Nakatsuji, S. Koeda, M. Hedo and Y. Uwatoko
  • Journal Title: Journal of the Physical Society of Japan Volume: 78 Pages: 094603-094604
  • Peer Reviewed
• [Journal Article] Possible Existence of Magnetic Polaron in Nearly Ferromagnetic Semiconductor β -US_2 (2009)
  • Author(s): S. Ikeda, H. Sakai, N. Tateiwa, T. D. Matsuda, D. Aoki, Y. Homma, E. Yamamoto, A. Nakamura, Y. Shiokawa, Y. Ota, K. Sugiyama, M. Hagiwara, K. Kindo, K. Matsubayashi, M. Hedo, Y. Uwatoko, Y. Haga and Y. Onuki
  • Journal Title: Journal of the Physical Society of Japan Volume: 78 Pages: 114704-114710
  • Peer Reviewed
• [Presentation] 圧力中におけるEuCoGe_3 の輸送特性 (2011)
  • Author(s): 平川先太郎, 渡部晋太郎, 照屋淳志, 竹田政貴, 辺土正人, 仲間隆男, 矢ヶ崎克馬, 高江洲義尚, 内間清晴, 松林和幸, 上床美也
  • Organizer: 高圧討論会(日本高圧力学会)
  • Place of Presentation: 沖縄キリスト教学院大学
  • Year and Date: 2011-11-10
• [Presentation] 鉄ヒ素系超伝導体の高圧下熱電能 (2011)
  • Author(s): 米須将太, 仲村愛, 新垣望, 瑞慶覧長潤, 竹田政貴, 高江洲義尚, 辺土正人, 仲間隆男, 内間清晴, 的場智広, 光田暁弘, 和田裕文
  • Organizer: 高圧討論会(日本高圧力学会)
  • Place of Presentation: 沖縄キリスト教学院大学
  • Year and Date: 2011-11-10
• [Presentation] EuFe2As_2 の高圧下の熱電能と電子状態 (2011)
  • Author(s): 米須将太, 仲村愛, 新垣望, 瑞慶覧長潤, 竹田政貴, 高江洲義尚, 辺土正人, 仲間隆男, 内間清晴, 的場智広, 光田暁弘, 和田裕文
  • Organizer: 日本物理学会
  • Place of Presentation: 富山大学
  • Year and Date: 2011-09-22
• [Presentation] Thermopower measurement under high pressure using "seesaw heating method" (2009)
  • Author(s): M. Hedo, D. Nakamura, Y. Takaesu, T. Fujiwara, K. Uchima, K. Yagasaki and T. Nakama
  • Organizer: International Conference on High Pressure Science and Tecchnology (AIRAPT-22)
  • Place of Presentation: Tokyo Japan
  • Year and Date: 2009-07-28