New Developments in the area of topological insulators

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Date/Time:Thursday, 30 Jan 2014 - Saturday, 01 Feb 2014
Location:PHYSICS Hall Room 5
Channel:Condensed Matter Physics
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Claudia Felser,
Max Planck Institute of Chemical Physics for Solids, Dresden,
and Johannes Gutenberg University, Mainz, Germany

Topological insulator are a hot topic in condensed matter physics. The excitement in the physics community is comparable with the excitement when a new superconductor is discovered. HgTe and other systems such as Heusler compounds have an s-p-band inversion at the Fermi edge which makes this family suitable for the Quantum Spin Hall effect and topological insulators [1]. A new topological insulators was identified in cerium-filled skutterudite (FS) compounds. We find that two compounds, CeOs4As12 and CeOs4Sb12, are zero gap materials with band inversions between Os-d and Ce-f orbitals. Both compounds are predicted to become topological Kondo insulators at low temperatures, which are Kondo insulators in the bulk but with robust Dirac surface states on the boundary [2]. In the actinide compounds 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 [3]. This is not so surprising since the SOC should be large in Actinides. 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. The superconductor BaKBiO3 (BKBO) with Tc nearly 30 K emerges as a TI in the electron-doped region, whereas it is a superconductor in the hole-doped region. BBO exhibits a large topological energy gap of 0.7 eV [4]. We will discuss the necessary and sufficient conditions for new TI materials, based in symmetry and bonding arguments [5].

1. S. Chadov, X. Qi, J. K?bler, G. H. Fecher, C. Felser, S.-C. Zhang, Nature Mater. 9, (2010) 541 "Tunable multifunctional topological insulators in ternary Heusler compounds"

2. B. Yan, L. M?chler, X.-L. Qi, S.-C. Zhang, C. Felser, Phys. Rev. B 85 (2012) 165125 "Topological insulators in filled skutterudites"

3. X. Zhang, HJ. Zhang, J. Wang, C. Felser, S.-C. Zhang, Science 335, (2012)1464 "Actinide Topological Insulator Materials with Strong Interaction"

4. Binghai Yan, Martin Jansen, Claudia Felser, A large energy-gap oxide topological insulator based on the superconductor BaBiO3, Nature Phys. (2013) accepted

5. L.M?chler, HJ. Zhang, S. Chadov, B. Yan, F. Casper, J. K?bler, SC. Zhang, C. Felser, Angew. Chem. Int. Ed. 51, (2012) 7221 "Topological Insulators from a Chemist's Perspective"