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Electronic Structure of YbB 6 : Is it a Topological Insulator or Not?

Title
Electronic Structure of YbB 6 : Is it a Topological Insulator or Not?
Authors
Chang-Jong KangDenlinger, JDAllen, JWChul-Hee MinReinert, FKang, BYCho, BKKang, JSShim, JHMIN, BYUNG IL
POSTECH Authors
Shim, JHMIN, BYUNG IL
Date Issued
2016-03
Publisher
American Physical Society
Abstract
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 similar to 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.
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 similar to 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.
URI
https://oasis.postech.ac.kr/handle/2014.oak/29966
DOI
10.1103/PHYSREVLETT.116.116401
ISSN
0031-9007
Article Type
Article
Citation
PHYSICAL REVIEW LETTERS, vol. 116, no. 11, page. 11640-1 - 11640-6, 2016-03
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심지훈SHIM, JI HOON
Div of Advanced Materials Science
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