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Title: Electronic structure of YbB6: Is it a topological insulator or not?

Here, to finally resolve the controversial issue of whether or not the electronic structure of YbB6 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 YbB6 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 YbB6 is investigated theoretically and found to transform into a p–d overlap semimetal with small Yb mixed valency.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5] ;  [5] ;  [6] ;  [1] ;  [1]
  1. Pohang Univ. of Science and Technology, (POSTECH) Pohang (Korea)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Univ. of Michigan, Ann Arbor, MI (United States)
  4. Univ. Wurzburg, Wurzburg (Germany)
  5. GIST, Gwangju (Korea)
  6. The Catholic Univ. of Korea, Bucheon (Korea)
Publication Date:
OSTI Identifier:
1332328
Report Number(s):
LBNL--1004709
Journal ID: ISSN 0031-9007; PRLTAO; ir:1004709
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 116; Journal Issue: 11; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Org:
Advanced Light Source Division; USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY ALS Beamline 4.0.3