title: Surface Kondo effect and non-trivial metallic state of the Kondo insulator YbB12.
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.
authors: Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan.
authors: Kenta
authors: K
authors: Hagiwara
authors: Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan.|Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan.
authors: Yoshiyuki
authors: Y
authors: Ohtsubo
authors: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
authors: Masaharu
authors: M
authors: Matsunami
authors: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
authors: Shin-Ichiro
authors: S
authors: Ideta
authors: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
authors: Kiyohisa
authors: K
authors: Tanaka
authors: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
authors: Hidetoshi
authors: H
authors: Miyazaki
authors: Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France.
authors: Julien E
authors: 0000-0002-2450-5535
authors: JE
authors: Rault
authors: Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France.
authors: Patrick Le
authors: PL
authors: Fèvre
authors: Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France.
authors: François
authors: F
authors: Bertran
authors: Synchrotron SOLEIL, Saint-Aubin-BP 48, F-91192 Gif sur Yvette, France.|UR1/CNRS-Synchrotron SOLEIL, Saint-Aubin, F-91192 Gif sur Yvette, France.
authors: Amina
authors: A
authors: Taleb-Ibrahimi
authors: Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan.
authors: Ryu
authors: R
authors: Yukawa
authors: Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan.
authors: Masaki
authors: M
authors: Kobayashi
authors: Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan.
authors: Koji
authors: K
authors: Horiba
authors: Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba 305-0801, Japan.
authors: Hiroshi
authors: H
authors: Kumigashira
authors: Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
authors: Kazuki
authors: K
authors: Sumida
authors: HiSOR, Hiroshima University, Higashi-Hiroshima 739-0046, Japan.
authors: Taichi
authors: T
authors: Okuda
authors: College of Science, Ibaraki University, Mito 310-8512, Japan.
authors: Fumitoshi
authors: F
authors: Iga
authors: Department of Physics, Graduate School of Science, Osaka University, Toyonaka 560-0043, Japan.|Graduate School of Frontier Biosciences, Osaka University, Suita 565-0871, Japan.
authors: Shin-Ichi
authors: S
authors: Kimura