スピン三重項超伝導体ルテニウム酸化物とそれを含む共晶体の一軸性圧力効果

• Project/Area Number: 08J00959
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: Biophysics/Chemical physics
• Research Institution: Kyoto University
• Principal Investigator: 橘高 俊一郎 Kyoto University, 大学院・理学研究科, 特別研究員(DC2)
• Project Period (FY): 2008 – 2009
• Project Status: Completed (Fiscal Year 2009)
• Budget Amount: ¥1,200,000 (Direct Cost: ¥1,200,000); Fiscal Year 2009: ¥600,000 (Direct Cost: ¥600,000); Fiscal Year 2008: ¥600,000 (Direct Cost: ¥600,000)
• Keywords: スピン三重項超伝導 / Sr2RuO4 / 共晶体 / 帯磁率測定 / 一軸性圧力

Research Abstract

Sr_2RuO_4-Ru共晶体では、Sr_2RuO_4の超伝導転移温度T_c(=1.5K)より約2倍高い3Kから界面超伝導を示すが、そのメカニズムは長年未解明であった。我々は、Sr_2RuO_4の異方的な結晶歪みがT_cの上昇に寄与していると考え、様々な方向の一軸性圧力下でSQUID磁束計(MPMS、最低到達温度1.8K)を用いてSr_2RuO_4-Ru共晶体の磁化測定を行った。その結果、静水圧力下ではSr_2RuO_4のT_cは減少するにもかかわらず、一軸性圧力を印加した共晶体ではいずれの方向においても1.8Kでのマイスナー信号が上昇し、その上昇は面内方向の圧力下で最も大きいことを明らかにした。一方、純粋なSr_2RuO_4はT_cが低いために、SQUID磁束計ではその超伝導転移は検出不可能であった。そこで、0.3Kの低温まで交流帯磁率を一軸性圧力下で測定可能な実験手法を開発し、純粋なSr_2RuO_4における超伝導の一軸性圧力効果を調べた。その結果、驚くべきことにSr_2RuO_4のc軸方向に0.2GPaの弱い一軸性圧力を印加することで、オンセットT_cが3.2Kの超伝導が誘起されることを発見した。この効果は、バンド計算やEhrenfestの関係式からこれまでに予想されていたSr_2RuO_4の一軸性圧力効果と質的・量的に異なっており、Sr_2RuO_4が異方的結晶歪みの有無によりT_c=1.5KとT_c～3Kという2つの超伝導相を元来有していることを示唆している。本研究により、長年研究されているSr_2RuO_4超伝導の新たな一面を見出すことに成功した。

Research Products

• [Journal Article] Uniaxial pressure effect on the superconductivity in the Sr3Ru2O7 region (2010)
  • Author(s): S.Kittaka, H.Yaguchi, Y.Maeno, R.Fittipaldi, A.Vecchione
  • Journal Title: Physica C (掲載決定)
  • Peer Reviewed
• [Journal Article] Spatial development of superconductivity in the Sr2RuO4-Ru eutectic system (2009)
  • Author(s): S.Kittaka, T.Nakamura, H.Yaguchi, S.Yonezawa, Y.Maeno
  • Journal Title: Journal of the Physical Society of Japan 78
  • Peer Reviewed
• [Journal Article] Towards intrinsic functionalities of bilayered ruthenate Sr3Ru2O7 (2009)
  • Author(s): R.Ciancio, J.Borjesson, H.Pettersson, R.Fittipaldi, D.Zola, A.Vecchione, M.Polichetti, S.Kittaka, Y.Maeno, S.Pace, E.Olsson
  • Journal Title: Physical Review B 80
  • Peer Reviewed
• [Journal Article] Atomic structure of functional interfaces in Sr2RuO4/Sr3Ru2O7 eutectic crystals (2009)
  • Author(s): R.Ciancio, J.Borjesson, H.Pettersson, S.Lopatin, R.Fittipaldi, A.Vecchione, S.Kittaka, Y.Maeno, S.Pace, E.Olsson
  • Journal Title: Applied Physics Letters 95
  • Peer Reviewed
• [Journal Article] Large Enhancement of 3-K Phase Superconductivity in the Sr2RuO4-Ru Eutectic System (2009)
  • Author(s): S.Kittaka, H.Yaguchi, Y.Maeno
  • Journal Title: Journal of the Physical Society of Japan 78
  • Peer Reviewed
• [Journal Article] Angular dependence of the upper critical field of Sr2RuO4 (2009)
  • Author(s): S.Kittaka, T.Nakamura, Y.Aono, S.Yonezawa, K.Ishida, Y.Maeno
  • Journal Title: Physical Review B 80
  • Peer Reviewed
• [Journal Article] Enhancement of interfacial superconductivity in the eutectic system Sr2RuO4-Ru by uniaxial pressure (2009)
  • Author(s): H. Yaguchi, S. Kittaka, Y. Maeno
  • Journal Title: Journal of Physics : Conference Series 150
  • Peer Reviewed
• [Journal Article] Superconducting behavior via percolation in Sr2RuO4-Sr3Ru2O7 eutectic crystals (2009)
  • Author(s): R. Fittipaldi, M. Cuoco, V. Granata, C. Noce, S. Pace, D. Stornaiuolo, D. Born, F. Tafuri, S. Kittaka, Y. Maeno, A. Vecchione
  • Journal Title: Journal of Physics : Conference Series 150
  • Peer Reviewed
• [Journal Article] Unusual temperature dependence of the in-plane critical field in Sr2RuO4 (2009)
  • Author(s): S. Kittaka, T. Nakamura, Y. Aono, S. Yonezawa, K. Ishida, Y. Maeno
  • Journal Title: Journal of Physics : Conference Series 150
  • Peer Reviewed
• [Journal Article] Evidence for the Sr2RuO4 intercalations in the Sr3Ru2O7 region of the Sr3Ru2O7-Sr2RuO4 eutectic system (2009)
  • Author(s): S. Kittaka, S. Yonezawa, H. Yaguchi, Y. Maeno, R. Fittipaldi, A. Vecchione, J. -F. Mercure, A. Gibbs, R. S. Perry, A. P. Mackenzie
  • Journal Title: Journal of Physics : Conference Series 150
  • Peer Reviewed
• [Journal Article] Spatial development of superconductivity in the Sr2RuO4-Ru eutectic system (2009)
  • Author(s): S. Kittaka, T. Nakamura, H. Yaguchi, S. Yonezawa, Y. Maeno
  • Journal Title: Journal of the Physical Society of Japan
  • Peer Reviewed
• [Journal Article] Multiple superconducting transitions in the Sr3Ru2O7 region of Sr3Ru2O7-Sr2RuO4 eutectic crystals (2008)
  • Author(s): S. Kittaka, S. Fusanobori, S. Yonezawa, H. Yaguchi, Y. Maeno, R. Fittipaldi, A. Vecchione
  • Journal Title: Physical Review B 77
  • Peer Reviewed
• [Journal Article] Superconductivity in Sr2RuO4-Sr3Ru2O7 eutectic crystals (2008)
  • Author(s): R. Fittipaldi, A. Vecchione, R. Ciancio, S. Pace, M. Cuoco, D. Stornaiuolo, D. Born, F. Tafuri, E. Olsson, S. Kittaka, H. Yaguchi, Y. Maeno
  • Journal Title: Europhysics Letter 83
  • Peer Reviewed
• [Presentation] Enhancement of Tc to 3K by applying uniaxial pressure to Sr2RuO4 (2010)
  • Author(s): 橘高俊一郎
  • Organizer: International Symposium on Physics of New Quantum Phases in Superclean Materials
  • Place of Presentation: 横浜
  • Year and Date: 2010-03-09
• [Presentation] ccurate and precise examination of the angular dependence of the upper critical field of Sr2RuO4 (2009)
  • Author(s): 橘高俊一郎
  • Organizer: Novel Spin Pairing 2009
  • Place of Presentation: 京都
  • Year and Date: 2009-09-14
• [Presentation] Uniaxial pressure effect on the superconductivity observed in the Sr3Ru2O7 region of the Sr3Ru2O7-Sr2RuO4 eutectic system (2009)
  • Author(s): 橘高俊一郎
  • Organizer: 9th International Conference on Materials and Mechanisms of Superconductivity
  • Place of Presentation: 東京
  • Year and Date: 2009-09-09
• [Presentation] Sr3Ru207-Sr2RuO4共晶系における多段階超伝導転移の一軸性圧力効果 (2009)
  • Author(s): 橘高俊一郎
  • Organizer: 日本物理学会第64回年次大会(口頭発表)
  • Place of Presentation: 立教大学
  • Year and Date: 2009-03-29
• [Presentation] 磁場方向精密制御下におけるSr2RuO4の上部臨界磁場角度依存 (2008)
  • Author(s): 橘高俊一郎
  • Organizer: 日本物理学会2008年秋季大会(口頭発表)
  • Place of Presentation: 岩手大学
  • Year and Date: 2008-09-23
• [Presentation] Unusual temperature dependence of in-plane critical field in Sr2RuO4 (2008)
  • Author(s): 橘高俊一郎
  • Organizer: 25th international conference on Low Temperature Physics (ポスター)
  • Place of Presentation: アムステルダム(オランダ)
  • Year and Date: 2008-08-08
• [Presentation] Evidence for the Sr2RuO4 intercalations in the Sr3Ru2O7 region of the Sr3Ru2O7-Sr2RuO4 eutectic system (2008)
  • Author(s): 橘高俊一郎
  • Organizer: 25th international conference on Low Temperature Physics (ポスター)
  • Place of Presentation: アムステルダム(オランダ)
  • Year and Date: 2008-08-08
• [Remarks] 研究者個人のページ
  • URL: http://sakaki.issp.u-tokyo.ac.jp/user/kittaka/index.html
• [Remarks] 所属研究機関のページ
  • URL: http://www.ss.scphys.kyoto-u.ac.jp/
• [Remarks] 研究者個人のページ
  • URL: http://www.ss.scphys.kyoto-u.ac.jp/person/kittaka/index.html
• [Remarks] 所属研究機関のページ
  • URL: http://www.ss.scphys.kyoto-u.ac.jp/