Emergent Phenomena Measurement Research Team

Principal Investigator

PI Name Tetsuo Hanaguri
Degree D.Eng.
Title Team Leader
Brief Resume
1993D.Eng., Tohoku University
1993Research Associate, Department of Basic Science, The University of Tokyo
1999Associate Professor, Department of Advanced Materials Science, The University of Tokyo
2004Senior Research Scientist, Magnetic Materials Laboratory, RIKEN
2013Team Leader, Emergent Phenomena Measurement Research Team, Strong Correlation Physics Division, RIKEN Center for Emergent Matter Science (-present)

Outline

We experimentally study electronic states related to emergent phenomena in electron systems, such as high-temperature superconductivity and topological quantum phenomena. For this purpose, we use scanning tunneling microscopes working under combined extreme conditions of very low temperatures, high magnetic fields and ultra-high vacuum. Modern scanning-tunneling-microscopy technology enables us to obtain a “map of the electronic state” with atomic-scale spatial resolution. We make and analyze the maps of various materials and establish the relationships between material properties and electronic states. We also pursue the development of novel measurement techniques to discover new emergent phenomena in condensed matter.

Research Fields

Physics, Engineering, Materials Science

Keywords

Scanning tunneling microscopy
Superconductivity
Topological insulators

Results

Direct imaging of massless electrons at the surface of a topological insulator

Topological insulators are a new phase of matter which was discovered recently. Although it is an insulator in the bulk, a topological insulator possesses a metallic surface where electrons lose their mass. The surface state is expected to serve as a base of spintronics application, because spins of massless electrons can be used to handle information. However, the experimental understanding of massless electrons is still elusive.

Using scanning tunneling microscope, our team succeeded in imaging the nano-scale spatial structure of massless electrons at the surface of a topological insulator Bi2Se3. We focus on imaging in a magnetic field, where electrons exhibit cyclotron motion. The center of the cyclotron motion drifts around the charged defect, resulting in an “electron ring”. We found that the unique character of massless electrons manifests itself in the internal structure of the electron ring. The observed internal structure is related to the spin distribution and will give us an important clue for future spintronics applications.

“Electron rings” at different energies.

Members

Tetsuo Hanaguri

Team Leader hanaguri[at]riken.jp R

Yuhki Kohsaka

Senior Research Scientist

Tadashi Machida

Senior Research Scientist

Christopher John Butler

Special Postdoctoral Researcher

Yuuki Yasui

Postdoctoral Researcher

Publications

  1. C. J. Butler, M. Yoshida, T. Hanaguri, and Y. Iwasa

    Mottness versus unit-cell doubling as the driver of the insulating state in 1T-TaS2

    Nat. Commun. 11, 2477 (2020)
  2. T. Machida, Y. Sun, S. Pyon, S. Takeda, Y. Kohsaka, T. Hanaguri, T. Sasagawa, and T. Tamegai

    Zero-energy vortex bound state in the superconducting topological surface state of Fe(SeTe)

    Nat. Mater. 18, 811 (2019)
  3. T. Hanaguri, S. Kasahara, J. Boeker, I. Eremin, T. Shibauchi, and Y. Matsuda

    Quantum Vortex Core and Missing Pseudogap in the Multiband BCS-BEC Crossover Superconductor FeSe

    Phys. Rev. Lett. 122, 077001 (2019)
  4. T. Machida, Y. Kohsaka, and T. Hanaguri

    A scanning tunneling microscope for spectroscopic imaging below 90 mk in magnetic fields up to 17.5 T

    Rev. Sci. Instrum. 89, 093707 (2018)
  5. T. Hanaguri, K. Iwaya, Y. Kohsaka, T. Machida, T. Watashige, S. Kasahara, T. Shibauchi, and Y. Matsuda

    Two distinct superconducting pairing states divided by the nematic end point in FeSe1-xSx

    Sci. Adv. 4, aar6419 (2018)

Articles