Topological insulators in the NaCaBi family with large spin-orbit coupling gaps

By means of first-principles calculations and crystal structure searching techniques, we predict that a different NaCaBi family crystallized into the ZrBeSi-type (i.e., P63/mmc) are strong topological insulators (STIs). Taking P63/mmc as an example, calculated band indicates there is inversion between two opposite-parity bands at Γ point. In contrast to well-known Bi2Se3 family, in has already occurred even without spin-orbit coupling (SOC), giving rise nodal ring surrounding kz=0 plane (protected by Mz symmetry). With time-reversal symmetry (T) (I), spinless nodal-line metallic phase protected [TI]2=1 weak-SOC limit spinful insulating phase. Upon including SOC, gapped, driving system STI. Besides symmetry, nontrivial topology can also be indicated 6¯ symmetry. More surprisingly, SOC-induced gap about 0.34 eV, which larger than energy scale room temperature. Four other compounds (KBaBi, KSrBi, RbBaBi, RbSrBi) stable ambient pressure, both thermodynamics lattice dynamics, though their gaps smaller NaCaBi. Thus, they provide good platforms study states theory experiments.4 MoreReceived 14 September 2020Accepted 23 February 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.013278Published American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution this work must maintain attribution author(s) published article's title, journal citation, DOI.Published SocietyPhysics Subject Headings (PhySH)Research AreasElectrical propertiesElectronic structureFermi surfaceFirst-principles calculationsSpin-orbit couplingSurface statesPhysical SystemsTopological insulatorsTopological materialsCondensed Matter & Materials Physics