View full-text article in PMC Nat Commun. 2020 Apr 30;11:2108. doi: 10.1038/s41467-020-15705-y Search in PMC Search in PubMed View in NLM Catalog Add to search Copyright and License information © The Author(s) 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. PMC Copyright notice Fig. 4. Topological classes of the second-order Wannier bands. a Diagram of the topological classes for the second-order Wannier bands as a function of λiγi,i=x,y,z. b–d Energy spectra of a finite lattice obtained from first-principle FEM studies with a topological phase in (px−z,−y,py−x,−z,pz−y,−x)=(12,0,12), c in (px−z,−y,py−x,−z,pz−y,−x)=(0,0,12), and d in (px−z,−y,py−x,−z,pz−y,−x)=(0,0,0).