Imaging unconventional topological insulators

• Project/Area Number: 26707016
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Partial Multi-year Fund
• Research Field: Condensed matter physics I
• Research Institution: Tohoku University
• Principal Investigator: Okada Yoshinori 東北大学, 原子分子材料科学高等研究機構, 助教 (00707656)
• Project Period (FY): 2014-04-01 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥28,730,000 (Direct Cost: ¥22,100,000、Indirect Cost: ¥6,630,000); Fiscal Year 2016: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2015: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000); Fiscal Year 2014: ¥25,610,000 (Direct Cost: ¥19,700,000、Indirect Cost: ¥5,910,000)
• Keywords: トポロジカル絶縁体 / 走査トンネル顕微鏡 / トンネル分光 / 物性物理 / 遷移金属酸化物 / 薄膜 / STM / 超伝導 / 酸化物薄膜 / 強相関電子系 / ＳＴＭ

Outline of Final Research Achievements

Topological insulator (TI) is a new class of quantum material, which cannot be simply classified neither metal, insulator, nor superconductor. TIs have been acquiring considerable attention in broad fields ranging from material science, condensed matter physics, high energy physics, and mathematics, after the theoretical prediction of its existence. Beyond previously known topological insulators, a new class of topological insulator called topological crystalline insulators (TCIs) provide exciting platform for exploring extraordinarily tunability of topologically protected Dirac electron. In this study, using spectroscopic scanning tunneling microscope, we clarified characteristic electronic states of TCI at the atomic scale.

Research Products

• [Int'l Joint Research] Illinoi University/Princeton University/Boston College(米国)
• [Int'l Joint Research] 国立清華大学(台湾)
• [Int'l Joint Research] National University of Singapore(シンガポール)
• [Int'l Joint Research] Boston College/Illinoi University/Princeton University(米国)
• [Int'l Joint Research] National University of Singapore(Singapore)
• [Int'l Joint Research] National Tsing Hua University(Taiwan)
• [Journal Article] Scanning tunneling spectroscopy of superconductivity on surfaces of LiTi2O4 (111) thin films (2017)
  • Author(s): Y Okada, Y Ando, R Shimizu, E Minamitani, S Shiraki, S Watanabe, and T. Hitosugi
  • Journal Title: Nature Communications Volume: 印刷中
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] “Nanoscale Determination of the Mass Enhancement Factor in Lightly-Doped Bulk Insulator PbSe” (2015)
  • Author(s): I. Zeljkovic, K. L. Scipioni, D. Walkup, Yoshinori Okada, Wenwen Zhou, R. Sankar, G. Chang, Y. J. Wang, H. Lin, A. Bansil, F. Chou, Z. Wang and V. Madhavan
  • Journal Title: Nature Communications Volume: 6 Issue: 1 Pages: 6559-6563
  • DOI: 10.1038/ncomms7559
  • Peer Reviewed / Open Access
• [Journal Article] "Transformation of Dirac Surface States across the Quantum Phase Transition in a Topological Crystalline Insulator" (2015)
  • Author(s): I. Zeljkovic★, Yoshinori Okada★, C. Y. Huang, R. Sankar, D. Walkup, W. Zhou, M. Serbyn, F. Chou, W. F. Tsai, H. Lin, A. Bansil, L. Fu, M. Z. Hasan, V. Madhavan (★equal contribution)
  • Journal Title: Nature Materials Volume: 14 Issue: 3 Pages: 318-324
  • DOI: 10.1038/nmat4215
  • Peer Reviewed
• [Journal Article] "Mapping the unconventional orbital texture in topological crystalline insulators " (2014)
  • Author(s): I. Zeljkovic★, Yoshinori Okada★, C. Y. Huang, R. Sankar, D. Walkup, W. Zhou, M. Serbyn, F. Chou, W. F. Tsai, H. Lin, A. Bansil, L. Fu, M. Z. Hasan, V. Madhavan (★equal contribution)
  • Journal Title: Nature Physics Volume: 10 Issue: 8 Pages: 572-577
  • DOI: 10.1038/nphys3012
  • Peer Reviewed
• [Journal Article] Electronic phase separation in the doped spin-orbit driven Mott phase of Sr3(Ir1-xRux)2O7 (2013)
  • Author(s): C. Dhital, T. Hogan, W. Zhou, X. Chen, Z. Ren, M. Pokharel, Yoshinori Okada, M. Heine, Wei Tian, Z. Yamani, C. Opeil, J. S. Helton, J. W. Lynn, Z. Wang, V. Madhavan, S. D. Wilson
  • Journal Title: Nature Communications Volume: 5 Issue: 1 Pages: 3377-3383
  • DOI: 10.1038/ncomms4377
  • Peer Reviewed
• [Presentation] Strong Zeeman effects in the Landau level spectrum of (InxBi1−x)2Se3 (2016)
  • Author(s): D. Walkup, W. Zhou, I. Zeljkovic, Yoshinori Okada, Z. Ren, K. Scipioni, S. Wilson, V. Madhavan
  • Organizer: American Physical Society
  • Place of Presentation: Baltimore (US)
  • Year and Date: 2016-03-14
• [Presentation] Visualization of quasiparticle interference on cubic perovskite oxide surface (2016)
  • Author(s): Yoshinori Okada
  • Organizer: Special symposium for American Vacuum Society (AVS) Taiwan Chapter focusing on 2D materials and topological insulators
  • Place of Presentation: Kaohsiung, (Taiwan)
  • Year and Date: 2016-01-25
  • Invited
• [Presentation] Scanning Tunneling Spectroscopy Investigations of Surface States in Topological Crystalline Insulators (2015)
  • Author(s): Yoshinori Okada
  • Organizer: 21st International Conference on Electronic Properties of Two-Dimensional Systems
  • Place of Presentation: 仙台国際センター（宮城県、仙台市）
  • Year and Date: 2015-07-26
  • Invited
• [Presentation] “Visualization of Quasiparticle Interference on the Surface of SrVO3 Film” (invited) (2015)
  • Author(s): Yoshinori Okada, R. T. Chang, R. Shimizu, G. Chang, S. Shiraki, H. T. Jeng, H. Lin, T. Hitosugi
  • Organizer: ICMAT2015 - the 8th Biennial International Conference on Materials for Advanced Technologies (シンガポール)
  • Place of Presentation: Singapore
  • Year and Date: 2015-06-28 – 2015-07-03
  • Invited
• [Presentation] “Visualization of quasiparticle interference on the surface of SrVO3 film” (2015)
  • Author(s): Yoshinori Okada, T. R. Chang, R. Shimizu, G. Chang, H. T. Jeng, S. Shiraki, H. Lin, T. Hitosugi
  • Organizer: Ａｍｅｒｉｃａｌ Ｐｈｙｓｉｃａｌ Ｓｏｃｉｅｔｙ， Ｍａｒｃｈ Ｍｅｅｔｉｎｇ (米国)
  • Place of Presentation: San Antonio, Texas
  • Year and Date: 2015-03-02 – 2015-03-06
• [Presentation] ”Scanning tunneling spectroscopy investigation of the topological phase transition in (Bi1-xInx)2Se3” (2015)
  • Author(s): D. Walkup, W. Zhou, I. Zeljkovic, Yoshinori Okada, Z. Ren, K. Scipioni, S. Wilson, V. Madhavan
  • Organizer: Ａｍｅｒｉｃａｌ Ｐｈｙｓｉｃａｌ Ｓｏｃｉｅｔｙ， Ｍａｒｃｈ Ｍｅｅｔｉｎｇ (米国)
  • Place of Presentation: San Antonio, Texas
  • Year and Date: 2015-03-02 – 2015-03-06
• [Presentation] ”Nanoscale Determination of the Mass Enhancement Factor in Lightly-Doped Bulk Insulator PbSe” (2015)
  • Author(s): K. Scipioni, I. Zeljkovic, D. Walkup, Yoshinori Okada, W. Zhou, R. Sankar, G. Chang, Y. J. Wang, H. Lin, A. Bansil, F. Chou, Z. Wang, V. Madhavan
  • Organizer: Ａｍｅｒｉｃａｌ Ｐｈｙｓｉｃａｌ Ｓｏｃｉｅｔｙ， Ｍａｒｃｈ Ｍｅｅｔｉｎｇ (米国)
  • Place of Presentation: San Antonio, Texas
  • Year and Date: 2015-03-02 – 2015-03-06
• [Presentation] “Direct visualization of atomic and electronic structure on perovskite oxide film surface” (invited) (2015)
  • Author(s): T. Ohsawa, K. Iwaya, Yoshinori Okada, R. Shimizu, S. Shiraki, T. Hitosugi,
  • Organizer: SPIE Photonics West OPTO (米国)
  • Place of Presentation: The Moscone Center, CA, US
  • Year and Date: 2015-02-07 – 2015-02-12
  • Invited
• [Presentation] ”STM probing of topological states” （Ｉｎｖｉｔｅｄ）） (2014)
  • Author(s): Ｙｏｓｈｉｎｏｒｉ Ｏｋａｄａ
  • Organizer: E-MRS 2014 FALL MEETING (ポーランド)
  • Place of Presentation: Warsaw University of Technology, Poland
  • Year and Date: 2014-09-15 – 2014-09-19
  • Invited