電界誘起２次元超伝導の物性開拓

• Project/Area Number: 15J07681
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: Condensed matter physics II
• Research Institution: The University of Tokyo
• Principal Investigator: 斎藤 優 東京大学, 工学系研究科, 特別研究員(DC1)
• Project Period (FY): 2015-04-24 – 2018-03-31
• Project Status: Completed (Fiscal Year 2017)
• Budget Amount: ¥3,400,000 (Direct Cost: ¥3,400,000); Fiscal Year 2017: ¥1,100,000 (Direct Cost: ¥1,100,000); Fiscal Year 2016: ¥1,100,000 (Direct Cost: ¥1,100,000); Fiscal Year 2015: ¥1,200,000 (Direct Cost: ¥1,200,000)
• Keywords: 超伝導 / 2次元物質 / 対称性の破れ / 量子相転移 / 熱電 / 黒リン / 2次元 / 量子ゆらぎ / 金属基底状態 / 巨大臨界磁場 / スピン軌道相互作用 / 強磁場

Outline of Annual Research Achievements

高結晶性2次元超伝導体[1]の特徴的な物性としてこれまで量子金属[2]や巨大な臨界磁場現象[3]を明らかにしてきたが、今回特別研究員は、同様の系であるMoS2とZrNClの電気二重層トランジスタにおいて、磁場下での詳細な電気抵抗測定を行うことで、量子相転移現象を包括的に明らかにするとともに超伝導非相反伝導現象の開拓を行った。前者においては、面直方向に磁場を印加することで電気抵抗と磁場の曲線に多数の量子臨界点を持つことを発見した[4]。これは各温度領域のおける有限サイズスケーリングによる解析の結果、量子グリフィス相という新奇な量子状態であることを示唆しており、量子金属状態から量子グリフィス状態へのクロスオーバーは高結晶性2次元超伝導体の普遍的な特徴ではないかと考えられる。後者の研究では、MoS2の電気二重層トランジスタでの超伝導転移付近で、3回対称性を反映した超伝導非相反現象を観測した[5]。これらの非相反伝導現象は超伝導と常伝導の間の領域で起こるため、ゆらぎによる電子対やvortexのラチェット的な運動が起源になっているのではないかと考えられる。これらの研究成果は新たに高結晶性2次元超伝導の学理を構築する上で重要な結果である。
[1] Y. Saito et al. Nature Rev. Mater. 2, 160094 (2016).
[2] Y. Saito et al. Science 350, 409 (2015).
[3] Y. Saito et al. Nature Physics 12, 144(2016).
[4] Y. Saito et al. Nature Communications 9, 778 (2018).
[5] R. Wakatsuki, Y. Saito et al. Science Advances 3, e1602390 (2017).

Research Progress Status

29年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

29年度が最終年度であるため、記入しない。

Research Products

• [Int'l Joint Research] University of Groningen(オランダ)
• [Journal Article] Quantum phase transitions in highly crystalline two-dimensional superconductors (2018)
  • Author(s): Saito Yu、Nojima Tsutomu、Iwasa Yoshihiro
  • Journal Title: Nature Communications Volume: 9 Issue: 1 Pages: 778-778
  • DOI: 10.1038/s41467-018-03275-z
  • Peer Reviewed / Open Access
• [Journal Article] Nonreciprocal charge transport in noncentrosymmetric superconductors (2017)
  • Author(s): Wakatsuki Ryohei、Saito Yu、Hoshino Shintaro、Itahashi Yuki M.、Ideue Toshiya、Ezawa Motohiko、Iwasa Yoshihiro、Nagaosa Naoto
  • Journal Title: Science Advances Volume: 3 Issue: 4
  • DOI: 10.1126/sciadv.1602390
  • Peer Reviewed / Open Access
• [Journal Article] Highly crystalline 2D superconductors (2016)
  • Author(s): Y. Saito, T. Nojima, Y. Iwasa
  • Journal Title: Nature Reviews Materials Volume: 2 Issue: 1
  • DOI: 10.1038/natrevmats.2016.94
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Gate-induced superconductivity in two-dimensional atomic crystals (2016)
  • Author(s): Y. Saito, T. Nojima, Y. Iwasa
  • Journal Title: Superconductor Science and Technology Volume: 29 Issue: 9 Pages: 093001-093001
  • DOI: 10.1088/0953-2048/29/9/093001
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Journal Article] Gate-Tuned Thermoelectric Power in Black Phosphorus (2016)
  • Author(s): Yu Saito, Takahiko Iizuka, Takashi Koretsune, Ryotaro Arita, Sunao Shimizu, Yoshihiro Iwasa
  • Journal Title: Nano Letters Volume: 16 Issue: 8 Pages: 4819-4824
  • DOI: 10.1021/acs.nanolett.6b00999
  • Peer Reviewed
• [Journal Article] Gate-optimized thermoelectric power factor in ultrathin WSe2 single crystals (2016)
  • Author(s): Masaro Yoshida, Takahiko Iizuka, Yu Saito, Masaru Onga, Ryuji Suzuki, Yijin Zhang, Yoshihiro Iwasa, Sunao Shimizu
  • Journal Title: Nano Letters Volume: 16 Issue: 3 Pages: 2061-2065
  • DOI: 10.1021/acs.nanolett.6b00075
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Superconductivity protected by spin-valley locking in ion-gated MoS2 (2016)
  • Author(s): Yu Saito, Yasuharu Nakamura, Mohammad Saeed Baharamy, Yoshimitsu Kohama, Yuichi Kasahara, Yuji Nakagawa, Masaru Onga, Masashi Tokunaga, Tsutomu Nojima, Youichi Yanase, and Yoshihiro Iwasa
  • Journal Title: Nature Physics Volume: 12 Issue: 2 Pages: 144-149
  • DOI: 10.1038/nphys3580
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Metallic ground state in an ion-gated two-dimensional superconductor (2015)
  • Author(s): Y. Saito, Y. Kasahara, J. T. Ye, Y. Iwasa, T. Nojima
  • Journal Title: Science Volume: 350 Issue: 6259 Pages: 409-413
  • DOI: 10.1126/science.1259440
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Superconductivity Series in Transition Metal Dichalcogenides by Ionic Gating (2015)
  • Author(s): W. Shi, J. T. Ye, Y. J. Zhang, R. Suzuki, M. Yoshida, J. Miyazaki, N. Inoue, Y. Saito, Y. Iwasa
  • Journal Title: Scientific Reports Volume: 5 Issue: 1 Pages: 12534-12534
  • DOI: 10.1038/srep12534
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Quantum phase transitions in highly crystalline 2D superconductors (2018)
  • Author(s): Yu Saito, Tsutomu Nojima, Yoshihiro Iwasa
  • Organizer: APS March Meeting 2018
  • Int'l Joint Research
• [Presentation] Nonreciprocal transport in superconducting MoS2 (2017)
  • Author(s): Y. Saito, R. Wakatsuki, S. Hoshino, T. Ideue, M. Ezawa, Y. Iwasa and N. Nagaosa
  • Organizer: The March Meeting 2017 of the American Physical Society
  • Place of Presentation: Ernest Morial Convention Center, NewOrleans, Louisiana, U.S.A.
  • Year and Date: 2017-03-15
  • Int'l Joint Research
• [Presentation] 2D superconductors without inversion symmetry (2017)
  • Author(s): Y. Saito
  • Organizer: CEMS-QPEC Topical Meeting on Superconductivity under Extreme Conditions
  • Place of Presentation: Faculty of Engineering Bldg. 6, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
  • Year and Date: 2017-01-17
  • Int'l Joint Research / Invited
• [Presentation] Highly crystalline 2D superconductors (2017)
  • Author(s): Yu Saito
  • Organizer: CEMS Topical Meeting on Emergent 2D Materials 2017
  • Int'l Joint Research / Invited
• [Presentation] 高結晶性2次元超伝導体 (2017)
  • Author(s): 斎藤優
  • Organizer: 超伝導研究の最先端: 多自由度・非平衡・電子相関・トポロジー・人工制御
  • Invited
• [Presentation] 高結晶性2次元超伝導体の量子相転移 (2017)
  • Author(s): 斎藤優、野島勉、岩佐義宏
  • Organizer: 日本物理学会2017年秋季大会
• [Presentation] Quantum phase transitions and symmetry-breaking physics in ion-gated 2D crystalline superconductors (2017)
  • Author(s): Yu Saito, Yoshihiro Iwasa
  • Organizer: Superthin 2017 Superconductivity in atomically thin materials and heterostructures
  • Int'l Joint Research / Invited
• [Presentation] Ion-gated 2D crystalline superconductors with broken inversion symmetry (2017)
  • Author(s): Yu Saito, Tsutomu Nojima, Yoshihiro Iwasa
  • Organizer: XXVI International Materials Research Congress 2017
  • Int'l Joint Research
• [Presentation] 2D crystalline superconductors with broken inversion symmetry (2017)
  • Author(s): Yu Saito
  • Organizer: 28th International Conference on Low Temperature Physics
  • Int'l Joint Research / Invited
• [Presentation] 2D crystalline superconductors based on transition metal dichalcogenides (2017)
  • Author(s): Yu Saito
  • Organizer: EMN Lyon meeting on 2D materials
  • Int'l Joint Research / Invited
• [Presentation] Highly crystalline 2D superconductors protected by spin-valley locking (2017)
  • Author(s): Yu Saito
  • Organizer: IEEE International Magnetics Conference INTERMAG Europe 2017
  • Int'l Joint Research / Invited
• [Presentation] Highly-crystalline 2D superconductors and beyond (2016)
  • Author(s): Y. Saito
  • Organizer: The 29th International Symposium on Superconductivity (ISS2016)
  • Place of Presentation: Tokyo International Forum, Chiyoda-ku, Tokyo, Japan
  • Year and Date: 2016-12-15
  • Int'l Joint Research / Invited
• [Presentation] 高結晶性を有する2次元超伝導体における量子相転移 (2016)
  • Author(s): 斎藤 優、野島 勉、岩佐 義宏
  • Organizer: 第24回渦糸物理国内会議
  • Place of Presentation: あきた芸術村・温泉ゆぽぽ（秋田県仙北市）
  • Year and Date: 2016-11-27
• [Presentation] MoS2電界誘起超伝導における非相反超伝導電流 (2016)
  • Author(s): 斎藤 優、井手上 敏也、岩佐 義宏
  • Organizer: 日本物理学会2016年秋季大会
  • Place of Presentation: 金沢大学角間キャンパス（石川県金沢市）
  • Year and Date: 2016-09-14
• [Presentation] ZrNCl電界誘起超伝導における量子Griffiths相 (2016)
  • Author(s): 斎藤 優、野島 勉、岩佐 義宏
  • Organizer: 日本物理学会2016年秋季大会
  • Place of Presentation: 金沢大学角間キャンパス（石川県金沢市）
  • Year and Date: 2016-09-13
• [Presentation] Quantum Griffiths singularity and associated quantum metal in highly-crystalline two-dimensional superconductors (2016)
  • Author(s): Y. Saito, T. Nojima, Y. Iwasa
  • Organizer: FET Workshop 2016
  • Place of Presentation: Ruttgers Bay Lake Lodge, Deerwood, Minnesota, U.S.A.
  • Year and Date: 2016-09-09
  • Int'l Joint Research
• [Presentation] Griffiths singularity of quantum phase transition in ion-gated ZrNCl (2016)
  • Author(s): Y. Saito, T. Nojima, Y. Iwasa
  • Organizer: American Physical Society March Meeting 2016
  • Place of Presentation: Baltimore convention center, Baltimore, Maryland U.S.A.
  • Year and Date: 2016-03-14
  • Int'l Joint Research
• [Presentation] Cooper pairing protected by spin-valley locking in two-dimensional superconductivity on MoS2 (2016)
  • Author(s): Y. Saito, Y. Nakamura, M. S. Bahramy, Y. Kohama, J. T. Ye, Y. Kasahara, M. Tokunaga, T. Nojima, Y. Yanase, Y. Iwasa
  • Organizer: American Physical Society March Meeting 2016
  • Place of Presentation: Baltimore convention center, Baltimore, Maryland U.S.A.
  • Year and Date: 2016-03-14
  • Int'l Joint Research
• [Presentation] Quantum creep in a highly crystalline two-dimensional superconductor (2016)
  • Author(s): Y. Saito, Y. Kasahara, J. T. Ye, Y. Iwasa, T. Nojima
  • Organizer: American Physical Society March Meeting 2016
  • Place of Presentation: Baltimore convention center, Baltimore, Maryland U.S.A.
  • Year and Date: 2016-03-14
  • Int'l Joint Research
• [Presentation] Noncentrosymmetric quasi-single-layer superconductivity in electrolyte-gated MoS2 (2016)
  • Author(s): Y. Saito, Y. Nakamura, M. S. Bahramy, Y. Kohama, Y. Kasahara, M. Tokunaga, T. Nojima, Y. Yanase, Y. Iwasa
  • Organizer: CEMS International Symposium on Supramolecular Chemistry & Functional Materials 2016
  • Place of Presentation: Ito hall, The University of Tokyo, Bunkyo-ku, Tokyo-to. Japan
  • Year and Date: 2016-01-13
  • Int'l Joint Research
• [Presentation] Two-dimensional superconductivity protected by spin-valley locking in ion-gated MoS2 (2015)
  • Author(s): Y. Saito, Y. Nakamura, M. S. Bahramy, Y. Kohama, Y. Kasahara, M. Tokunaga, T. Nojima, Y. Yanase and Y. Iwasa
  • Organizer: CEMS Topical Meeting on Emergent 2D Materials
  • Place of Presentation: Ohkouch hall, RIKEN, Wako-shi, Saitama-ken, Japan
  • Year and Date: 2015-12-11
  • Int'l Joint Research
• [Presentation] Electron transport in ion-gated black phosphorus (2015)
  • Author(s): Y. Saito, T. Iizuka, T. Koretsune, R. Arita and Y. Iwasa
  • Organizer: CEMS Topical Meeting on Emergent 2D Materials
  • Place of Presentation: Ohkouch hall, RIKEN, Wako-shi, Saitama-ken, Japan
  • Year and Date: 2015-12-11
  • Int'l Joint Research
• [Presentation] 黒リンナノ薄膜における電界誘起両極性金属絶縁体転移 (2015)
  • Author(s): 斎藤 優、岩佐 義宏
  • Organizer: 日本物理学会2015年秋季大会
  • Place of Presentation: 大阪府吹田市（関西学院大学千里山キャンパス）
  • Year and Date: 2015-09-16
• [Presentation] 2次元物質における電界誘起超伝導のエキゾチック物性 (2015)
  • Author(s): 斎藤 優、中村 康晴、モハマド・サイード・バハラミー、小濱 芳光、笠原 裕一、 叶 劍挺、徳永 将史、柳瀬 陽一、野島 勉、岩佐 義宏
  • Organizer: 日本物理学会2015年秋季大会
  • Place of Presentation: 大阪府吹田市（関西学院大学千里山キャンパス）
  • Year and Date: 2015-09-16
• [Presentation] Ion-gated interface superconductivity in two-dimensional layered materials (2015)
  • Author(s): Y. Saito
  • Organizer: Nordita program PILS 2015 Physics of Interfaces and Layered Structures
  • Place of Presentation: Nordita, Stockholm, Sweden
  • Year and Date: 2015-08-24
  • Int'l Joint Research / Invited
• [Presentation] Exotic phenomena in ion-gated two-dimensional superconductors (2015)
  • Author(s): Y. Saito, Y. Nakamura, M. S. Bahramy, Y. Kohama, Y. Kasahara, M. Tokunaga, T. Nojima, Y. Yanase and Y. Iwasa
  • Organizer: PILS 2015, Physics of Interfaces and Layered Structures
  • Place of Presentation: Nordita, Stockholm, Sweden
  • Year and Date: 2015-08-24
  • Int'l Joint Research
• [Presentation] Exotic superconducting states in ion-gated two-dimensional materials (2015)
  • Author(s): Y. Saito, Y. Nakamura, M. S. Bahramy, Y. Kohama, Y. Kasahara, M. Tokunaga, T. Nojima, Y. Yanase and Y. Iwasa
  • Organizer: M2S 2015, The11th International Conference on Materials & Mechanism of Superconductivity
  • Place of Presentation: Geneva International Conference Center, Geneve, Switzerland
  • Year and Date: 2015-08-23
  • Int'l Joint Research
• [Presentation] Interface superconductivity protected by valley-spin polarization in gate-tuned MoS2 (2015)
  • Author(s): Y. Saito, Y. Nakamura, M. S. Bahramy, Y. Kohama, Y. Kasahara, M. Tokunaga, T. Nojima, Y. Yanase and Y. Iwasa
  • Organizer: EP2DS21/MSS-17 Joint conference: 21st International Conference on Electronic Properties of Two-Dimensional Systems/17th International Conference on Modulated Semiconductor Structures
  • Place of Presentation: Sendai international center, Sendai-shi, Miyagi-ken, Japan
  • Year and Date: 2015-07-26
  • Int'l Joint Research
• [Presentation] Ambipolar insulator-to-metal transition and elecric-field-control thermoelectric properties in black phosphorus (2015)
  • Author(s): Y. Saito, T. Iizuka and Y. Iwasa
  • Organizer: NT15 The Sixteenth International Conference on the Science and Application of Nanotubes
  • Place of Presentation: Nagoya University, Nagoya-shi, Aichi-ken, Japan
  • Year and Date: 2015-06-29
  • Int'l Joint Research
• [Remarks] 研究員の業績
  • URL: http://iwasa.t.u-tokyo.ac.jp/CV_Yu_Saito_jp.html