Graduate School of Frontier Biosciences, Osaka University


Surface Kondo Effect and Non-Trivial Metallic State of the Kondo Insulator YbB12

Journal Nat Commun 7, 12690 (2016)
Authors Kenta Hagiwara (1), Yoshiyuki Ohtsubo (1, 2), Masaharu Matsunami (3), Shin-ichiro Ideta (3), Kiyohisa Tanaka (3), Hidetoshi Miyazaki (3), Julien Rault (4), Patrick Le Fèvre (4), François Bertran (4), Amina Taleb-Ibrahimi (4, 5), Ryu Yukawa (6), Masaki Kobayashi (6), Koji Horiba (6), Hiroshi Kumigashira (6), Kazuki Sumida (7), Taichi Okuda (8), Fumitoshi Iga (9) and Shin-ichi Kimura (1, 2)
  1. Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan
  2. Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan
  3. UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
  4. Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France
  5. UR1/CNRS-Synchrotron SOLEIL, Saint-Aubin, F-91192 Gif sur Yvette, France
  6. Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan
  7. Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
  8. HiSOR, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
  9. College of Science, Ibaraki University, Mito 310-8512, Japan
Title Surface Kondo Effect and Non-Trivial Metallic State of the Kondo Insulator YbB12
PubMed 27576449
Laboratory Photophysics Laboratory 〈Prof. Kimura〉
Abstract A synergistic effect between strong electron correlation and spin–orbit interaction has been theoretically predicted to realize new topological states of quantum matter on Kondo insulators (KIs), so-called topological Kondo insulators (TKIs). One TKI candidate has been experimentally observed on the KI SmB6(001), and the origin of the surface states (SS) and the topological order of SmB6 has been actively discussed. Here, we show a metallic SS on the clean surface of another TKI candidate YbB12(001) using angle-resolved photoelectron spectroscopy. The SS shows temperature-dependent reconstruction corresponding to the Kondo effect observed for bulk states. Despite the low-temperature insulating bulk, the reconstructed SS with c–f hybridization is metallic, forming a closed Fermi contour surrounding on the surface Brillouin zone and agreeing with the theoretically expected behaviour for SS on TKIs. These results demonstrate the temperature-dependent holistic reconstruction of two-dimensional states localized on KIs surface driven by the Kondo effect.
Description Topological Kondo insulator (TKI) phase of Ytterbium dodecaboride (YbB12) single crystal is discovered on the atomically-flat and well-ordered clean surface of its single crystal by K. Hagiwara, Y. Ohtsubo, S. Kimura (Osaka univ.), A. Taleb (Synchrotron SOLEIL), H. Kumigashira (KEK), T. Okuda (HiSOR), F. Iga (Ibaraki univ.) and their colleagues. They developed a technique of clean surface preparation of YbB12 and observed the fine electronic structure (dispersion, spin/orbital angular momentum) of the surface electronic state. The result clearly indicates that the theoretically-predicted TKI phase is realized in the YbB12 single crystal. This achievement would be applicable for future spintronic devices as a source of dissipation-less transport and/or high-speed switching.