RT Journal Article
SR Electronic
T1 Non-Abelian band topology in noninteracting metals
JF Science
JO Science
FD American Association for the Advancement of Science
SP 1273
OP 1277
DO 10.1126/science.aau8740
VO 365
IS 6459
A1 Wu, QuanSheng
A1 Soluyanov, Alexey A.
A1 Bzdušek, Tomáš
YR 2019
UL http://science.sciencemag.org/content/365/6459/1273.abstract
AB Band structure degeneracies in topological materials can take the form of lines or even chains of interconnected loops. Wu et al. study theoretically these nodal lines and how they evolve as the system parameters are varied. They focus on a class of materials that have weak spin-orbit coupling and that respect a combination of inversion- and time-reversal symmetry. Noncommutative topological charges are associated with nodal lines in such materials that place constraints on the configurations of these lines. Calculations indicate that elemental scandium under strain may provide a test system for this unconventional topology.Science, this issue p. 1273Electron energy bands of crystalline solids generically exhibit degeneracies called band-structure nodes. Here, we introduce non-Abelian topological charges that characterize line nodes inside the momentum space of crystalline metals with space-time inversion (𝒫𝒯) symmetry and with weak spin-orbit coupling. We show that these are quaternion charges, similar to those describing disclinations in biaxial nematics. Starting from two-band considerations, we develop the complete many-band description of nodes in the presence of 𝒫𝒯 and mirror symmetries, which allows us to investigate the topological stability of nodal chains in metals. The non-Abelian charges put strict constraints on the possible nodal-line configurations. Our analysis goes beyond the standard approach to band topology and implies the existence of one-dimensional topological phases not present in existing classifications.