TY - JOUR
T1 - Beyond Dirac and Weyl fermions
T2 - Unconventional quasiparticles in conventional crystals
AU - Bradlyn, Barry
AU - Cano, Jennifer
AU - Wang, Zhijun
AU - Vergniory, M. G.
AU - Felser, C.
AU - Cava, R. J.
AU - Bernevig, B. Andrei
N1 - Funding Information:
The authors thank A. Alexandradinata, T. Neupert, A. Soluyanov, and A. Yazdani for helpful discussions. M.G.V. acknowledges the Fellow Gipuzkoa Program through Fondo Europeo de Desarrollo Regional Una Manera de hacer Europa and the FIS2013-48286-C2-1-P national project of the Spanish Ministerio de Economía y Competitividad. B.A.B. acknowledges the support of the Army Research Office (ARO) Multidisciplinary University Research Initiative (MURI) on topological insulators, grant W911-NF-12-1-0461, ONR-N00014-11-1-0635, NSF CAREER DMR-0952428, NSF-Materials Research Science and Engineering Center (MRSEC) DMR-1005438, the Packard Foundation. and a Keck grant. R.J.C. similarly acknowledges the support of the ARO MURI and the NSF MRSEC grants. The authors declare no competing interest.
Publisher Copyright:
© 2016, American Association for the Advancement of Science. All rights reserved.
PY - 2016/8/5
Y1 - 2016/8/5
N2 - In quantum field theory, we learn that fermions come in three varieties: Majorana, Weyl, and Dirac. Here, we show that in solid-state systems this classification is incomplete, and we find several additional types of crystal symmetry-protected free fermionic excitations. We exhaustively classify linear and quadratic three-, six-, and eight-band crossings stabilized by space group symmetries in solid-state systems with spin-orbit coupling and time-reversal symmetry. Several distinct types of fermions arise, differentiated by their degeneracies at and along high-symmetry points, lines, and surfaces. Some notable consequences of these fermions are the presence of Fermi arcs in non-Weyl systems and the existence of Dirac lines. Ab initio calculations identify a number of materials that realize these exotic fermions close to the Fermi level.
AB - In quantum field theory, we learn that fermions come in three varieties: Majorana, Weyl, and Dirac. Here, we show that in solid-state systems this classification is incomplete, and we find several additional types of crystal symmetry-protected free fermionic excitations. We exhaustively classify linear and quadratic three-, six-, and eight-band crossings stabilized by space group symmetries in solid-state systems with spin-orbit coupling and time-reversal symmetry. Several distinct types of fermions arise, differentiated by their degeneracies at and along high-symmetry points, lines, and surfaces. Some notable consequences of these fermions are the presence of Fermi arcs in non-Weyl systems and the existence of Dirac lines. Ab initio calculations identify a number of materials that realize these exotic fermions close to the Fermi level.
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U2 - 10.1126/science.aaf5037
DO - 10.1126/science.aaf5037
M3 - Article
C2 - 27445310
AN - SCOPUS:84980349556
SN - 0036-8075
VL - 353
JO - Science
JF - Science
IS - 6299
M1 - aaf5037
ER -