δ-Bonding and Spin-Orbit Coupling Make SrAg 4 Sb 2 a Topological Insulator

Bonding interactions and spin-orbit coupling in the topological insulator SrAg Sb are investigated using DFT with orbital projection analysis. Ag-Ag delta bonding is a key ingredient in the topological insulating state because the delta antibonding band forms a band inversion with the 5 s sigma bond...

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Bibliographic Details
Published inChemistry : a European journal Vol. 30; no. 17; p. e202303679
Main Authors Morgan, H W T, Laderer, W T, Alexandrova, A N
Format Journal Article
LanguageEnglish
Published Germany 20.03.2024
Subjects
Intermetallic phases
Transition metals
Ab initio calculations
Topology
Bond theory
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Summary:Bonding interactions and spin-orbit coupling in the topological insulator SrAg Sb are investigated using DFT with orbital projection analysis. Ag-Ag delta bonding is a key ingredient in the topological insulating state because the delta antibonding band forms a band inversion with the 5 s sigma bonding band. Spin-orbit coupling is required to lift d orbital degeneracies and lower the antibonding band enough to create the band inversion. These bonding effects are enabled by a longer-than-covalent Ag-Ag distance in the crystal lattice, which might be a structural characteristic of other transition metal based topological insulators. A simplified model of the topological bands is constructed to capture the essence of the topological insulating state in a way that may be engineered in other materials.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.202303679