title: Electronic Structure of YbB_{6}: Is it a Topological Insulator or Not?
abstract: To finally resolve the controversial issue of whether or not the electronic structure of YbB_{6} is nontrivially topological, we have made a combined study using angle-resolved photoemission spectroscopy (ARPES) of the nonpolar (110) surface and density functional theory (DFT). The flat-band conditions of the (110) ARPES avoid the strong band bending effects of the polar (001) surface and definitively show that YbB_{6} has a topologically trivial B 2p-Yb 5d semiconductor band gap of ∼0.3  eV. Accurate determination of the low energy band topology in DFT requires the use of a modified Becke-Johnson exchange potential incorporating spin-orbit coupling and an on-site Yb 4f Coulomb interaction U as large as 7 eV. The DFT result, confirmed by a more precise GW band calculation, is similar to that of a small gap non-Kondo nontopological semiconductor. Additionally, the pressure-dependent electronic structure of YbB_{6} is investigated theoretically and found to transform into a p-d overlap semimetal with small Yb mixed valency.
authors.affiliation: Department of Physics, PCTP, Pohang University of Science and Technology, (POSTECH) Pohang 37673, Korea.
authors.forename: Chang-Jong
authors.initials: CJ
authors.lastname: Kang
authors.affiliation: Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, California 94720, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Denlinger
authors.affiliation: Department of Physics, Randall Laboratory, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Allen
authors.affiliation: Universität Würzburg, Experimentelle Physik VII, 97074 Würzburg, Germany.
authors.forename: Chul-Hee
authors.initials: CH
authors.lastname: Min
authors.affiliation: Universität Würzburg, Experimentelle Physik VII, 97074 Würzburg, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Reinert
authors.affiliation: School of Materials Science and Engineering, GIST, Gwangju 61005, Korea.
authors.forename: B Y
authors.initials: BY
authors.lastname: Kang
authors.affiliation: School of Materials Science and Engineering, GIST, Gwangju 61005, Korea.
authors.forename: B K
authors.initials: BK
authors.lastname: Cho
authors.affiliation: Department of Physics, The Catholic University of Korea, Bucheon 14662, Korea.
authors.forename: J-S
authors.initials: JS
authors.lastname: Kang
authors.affiliation: Department of Physics, PCTP, Pohang University of Science and Technology, (POSTECH) Pohang 37673, Korea.|Department of Chemistry and Division of Advanced Nuclear Engineering, POSTECH, Pohang 37673, Korea.
authors.forename: J H
authors.initials: JH
authors.lastname: Shim
authors.affiliation: Department of Physics, PCTP, Pohang University of Science and Technology, (POSTECH) Pohang 37673, Korea.
authors.forename: B I
authors.initials: BI
authors.lastname: Min