title: Proving Nontrivial Topology of Pure Bismuth by Quantum Confinement.
abstract: The topology of pure Bi is controversial because of its very small (∼10  meV) band gap. Here we perform high-resolution angle-resolved photoelectron spectroscopy measurements systematically on 14-202 bilayer Bi films. Using high-quality films, we succeed in observing quantized bulk bands with energy separations down to ∼10  meV. Detailed analyses on the phase shift of the confined wave functions precisely determine the surface and bulk electronic structures, which unambiguously show nontrivial topology. The present results not only prove the fundamental property of Bi but also introduce a capability of the quantum-confinement approach.
authors.affiliation: Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Ito
authors.affiliation: Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: B
authors.initials: B
authors.lastname: Feng
authors.affiliation: Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Arita
authors.affiliation: Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Takayama
authors.affiliation: Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: R-Y
authors.initials: RY
authors.lastname: Liu
authors.affiliation: Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Someya
authors.affiliation: National Synchrotron Radiation Research Center (NSRRC), Hsinchu, Taiwan 30076, Republic of China.
authors.forename: W-C
authors.initials: WC
authors.lastname: Chen
authors.affiliation: Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Iimori
authors.affiliation: Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Namatame
authors.affiliation: Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, Higashi-Hiroshima, Hiroshima 739-0046, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Taniguchi
authors.affiliation: National Synchrotron Radiation Research Center (NSRRC), Hsinchu, Taiwan 30076, Republic of China.
authors.forename: C-M
authors.initials: CM
authors.lastname: Cheng
authors.affiliation: National Synchrotron Radiation Research Center (NSRRC), Hsinchu, Taiwan 30076, Republic of China.|Department of Physics and Astronomy, National Tsing Hua University, Hsinchu, Taiwan 30013, Republic of China.
authors.forename: S-J
authors.initials: SJ
authors.lastname: Tang
authors.affiliation: Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Komori
authors.affiliation: Department of Physics, Ochanomizu University, Bunkyo-ku, Tokyo 112-8610, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: T-C
authors.initials: TC
authors.lastname: Chiang
authors.affiliation: Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Matsuda