Publication Date:
2016-04-15
Description:
Spatial symmetries in crystals may be distinguished by whether they preserve the spatial origin. Here we study spatial symmetries that translate the origin by a fraction of the lattice period, and find that these non-symmorphic symmetries protect an exotic surface fermion whose dispersion relation is shaped like an hourglass; surface bands connect one hourglass to the next in an unbreakable zigzag pattern. These 'hourglass' fermions are formed in the large-gap insulators, KHgX (X = As, Sb, Bi), which we propose as the first material class whose band topology relies on non-symmorphic symmetries. Besides the hourglass fermion, another surface of KHgX manifests a three-dimensional generalization of the quantum spin Hall effect, which has previously been observed only in two-dimensional crystals. To describe the bulk topology of non-symmorphic crystals, we propose a non-Abelian generalization of the geometric theory of polarization. Our non-trivial topology originates from an inversion of the rotational quantum numbers, which we propose as a criterion in the search for topological materials.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wang, Zhijun -- Alexandradinata, A -- Cava, R J -- Bernevig, B Andrei -- England -- Nature. 2016 Apr 14;532(7598):189-94. doi: 10.1038/nature17410.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, Princeton University, Princeton, New Jersey 08544, USA. ; Department of Physics, Yale University, New Haven, Connecticut 06520, USA. ; Department of Chemistry, Princeton University, Princeton, New Jersey 08540, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27075096" target="_blank"〉PubMed〈/a〉
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
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Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
