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C. Felser, M. Jansen, SC Zhang, L. Müchler, S. Chadov, B. Yan, J. Kübler, HJ Zhang
Topological insulators are a hot topic in condensed matter physics. Many Heusler compounds with C1b structure are ternary semiconductors that are structurally and electronically related to the binary semiconductors. The diversity of Heusler materials opens wide possibilities for tuning the bandgap and setting the desired band inversion by choosing compounds with appropriate hybridization strength (by the lattice parameter) and magnitude of spin-orbit coupling (SOC, by the atomic charge). Based on first-principle calculations we demonstrate that around 50 Heusler compounds show band inversion similar to that of HgTe [1]. Many of these ternary zero-gap semiconductors (LnAuPb, LnPdBi, LnPtSb and LnPtBi) contain the rare-earth element Ln, which can realize additional properties ranging from superconductivity (for example LaPtBi) to magnetism (for example GdPtBi) and heavy fermion behaviour (for example YbPtBi). These properties can open new research directions in realizing the quantized anomalous Hall effect and topological superconductors. In AmN and PuTe a band gap is opened by correlation effects. In a family of semiconductors with the simple NaCl structure band gaps up to 0.4 eV were found [2]. This is not so surprising since the SOC should be large in Actinides. Heusler compounds are similar to a stuffed diamond, correspondingly, it should be possible to find the "high Z"' equivalent of graphene in a graphite-like structure or in other related structure types with 18 valence electrons and with inverted bands [3]. Indeed the ternary compounds, such as LiAuSe and KHgSb with a honeycomb structure of their Au-Se and Hg-Sb layers feature band inversion very similar to HgTe which is a strong precondition for existence of the topological surface states [4,5]. LiAuSe is a strong TI, whereas KHgSb a weak TI. Up to now there are no oxides which were identified to be topological insulators. BaBiO3 is an oxide which shows a band inversion similar to HgTe. We will discuss the necessary and sufficient conditions for new TI materials, based in symmetry and bonding arguments [3]. 1. S. Chadov, X. Qi, J. Kübler, G. H. Fecher, C. Felser, S.-C. Zhang, Nature Mater. 2010, 9, 541 "Tunable multifunctional topological insulators in ternary Heusler compounds" 2. X. Zhang, HJ. Zhang, J. Wang, C. Felser, S.-C. Zhang, Science 2012, 335, 1464 "Actinide Topological Insulator Materials with Strong Interaction" 3. L. Müchler, HJ. Zhang, S. Chadov, B. Yan, F. Casper, J. Kübler, SC. Zhang, C. Felser, Angew. Chem. Int. Ed. 2012, 51, 7221 "Topological Insulators from a Chemist’s Perspective" 4. B. Yan, L. Müchler, C. Felser, Phys. Rev. Lett. 2012, 109, 116406 "Prediction of weak topological insulators in layered semiconductors" 5. H.-J. Zhang, S. Chadov, L. Müchler, B. Yan, XL. Qi, J. Kübler, SC. Zhang, C. Felser, Phys. Rev. Lett. 2011, 106, 156402 "Topological Insulators in Ternary Compounds with a Honeycomb lattice" 6. B. Yan, L. Müchler, X.-L. Qi, S.-C. Zhang, C. Felser, Phys. Rev. B 2012, 85, 165125 "Topological insulators in filled skutterudites" |
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