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Different Topological Quantum States in Ternary Zintl compounds: BaCaX (X = Si, Ge, Sn and Pb)

TitleDifferent Topological Quantum States in Ternary Zintl compounds: BaCaX (X = Si, Ge, Sn and Pb)
Publication TypeJournal Article
Year of Publication2018
AuthorsWang, LL, Kaminski, A, Canfield, PC, Johnson, DD
JournalJournal of Physical Chemistry C
Date Published01
Type of ArticleArticle
ISBN Number1932-7447
Accession NumberWOS:000422814200075
Keywordschemistry, insulator, Materials Science, metal, phase, scheme, simple, single dirac cone, surface-band calculations, Technology - Other Topics, total-energy calculations, transition, wannier functions, wave basis-set, weyl semimetal

Topological quantum states require stringent combination of crystal symmetry and spin-orbit coupling (SOC) strength. Here, we report that the ternary Zintl compound series BaCaX (X = Si, Ge, Sn and Pb, Group IV) in the same crystal structure having eight valence electrons per formula unit can host two different topological quantum phases, controlled by atomic size and SOC strength. BaCaSi is a nodal line semimetal (NLSM) with band inversion protected by mirror symmetry and hosts a strong topological insulator (TI) state when SOC is turned on; thus, a NLSM-TI phase. Moving to larger atomic sizes and heavier atoms, BaCaGe and BaCaSn are normal insulators (NIs); then, with the strongest SOC in BaCaPb, a different band inversion is induced; giving a strong TI phase without the need of NLSM. Thus, we also predict two types of topological transitions in a phase diagram for BaCaX: (1) NLSM-TI to NI, then to TI by tuning atomic size and SOC strength via alloying, and (2) NI or TI to NLSM-TI via pressure.

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