SPP 1666:  Topological Insulators: Materials - Fundamental Properties - Devices

• Subject Area: Physics
• Term: from 2013 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 220179758

The discoveries of the quantum spin Hall effect and of topological insulators (TI) have established a new material class in two and three dimensions. Topological insulators are materials, which are bulk insulators but exhibit conducting topologically protected surface states. Currently, for only few materials the electronic band structure of a TI has been demonstrated, and even less systems show experimentally accessible surface states, despite the fact that the number of predicted TI materials is constantly increasing. In order to progress in the field of TI, the following research areas are addressed with high priority and strong expertise: (1) Understanding and improvement of existing TI materials: Current materials (heterostructures of HgTe/Cd1-xHgxTe and surfaces of Bi1-xSbx, Bi2Te3, Bi2Se3, Sb2Te3, including their ternery and quaternary compounds) exhibit either a very small band gap or an intrinsic doping level that keeps the bulk in a metallic state. These materials shall be improved to enable room temperature applications involving the one- or two-dimensional surface state. This will require investigations of growth and the spacial and electronic structure. (2) Fundamental properties and devices: The fundamental properties of TI provide a large variety of extraordinary electronic characteristics such as forbidden backscattering. It is essential to explore these properties in order to provide a complete understanding of TI materials, which is necessary for the development of device structures and measurement techniques, in particular for spin-dependent transport, which will serve as precursors for future applications. (3) New Materials: New materials (e. g. Heusler compounds, oxides) help to overcome deficits of current materials and will add new properties. Innovative concepts, e.g., for detection of Majorana fermions based on TI, shall be developed. This Priority Programme brings together research groups within Germany working on TI, in particular experimentally and theoretically focussed research groups.

• DFG Programme: Priority Programmes
• International Connection: Denmark, Luxembourg, Russia, Spain

Projects

• Controlled charge and spin currents in surface states of a toplogical insulator (Applicant Buhmann, Hartmut )
• Coordination Funds (Applicant Rader, Oliver )
• Correlation of geometric and electronic structure at surfaces and interfaces of adsorbate covered topological insulators (Applicant Meyerheim, Holger L. )
• Current induced spin polarization in 3D topological insulator thin films (Applicant Burghard, Marko Klaus )
• Cyclotron resonance induced photocurrents and opto-electronic characterization of 2D and 3D topological insulators (Applicant Ganichev, Sergey )
• DFT+DMFT Investigation of Strongly Correlated Topological Materials (Applicant Zhang, Ph.D., Hongbin )
• Fermi Level Tuning by Low Temperature Atomic Layer Deposition/Epitaxy (ALD/ALE) of Ternary Chalcogenide Layers (Applicants Schulz, Stephan ;  Zierold, Robert )
• Fingerprint of surface and bulk states in transport of 3D topological insulators (Applicant Hankiewicz, Ewelina M. )
• First-principles studies of electronic and transport properties of one-dimensional edge states of nano-structured topological insulators (Applicant Bihlmayer, Gustav )
• InAs/GaSb/AlSB 2D topological insulator materials and devices (Applicant Kamp, Martin )
• Induced superconductivity in HgTe nanowires (Applicant Molenkamp, Laurens W. )
• Interacting Topological Insulators (Applicant Thomale, Ronny )
• Interfacing superconductors and ferromagnets with topological insulators using all in-situ/ultra high vacuum processes (Applicant Tjeng, Liu Hao )
• Investigation of directional THz spin currents in topological surface states (Applicants Heiliger, Christian ;  Kampfrath, Tobias ;  Münzenberg, Markus )
• Low-dimensional optoelectronic dynamics in 3D topological insulators (Applicant Holleitner, Alexander Walter )
• Magnetically doped topological insulators: From the Ground State to Dynamics (Applicants Ebert, Hubert ;  Fischer, Saskia F. ;  Rader, Oliver )
• Magnetotransport in magnetically doped topological insulators (Applicant Molenkamp, Laurens W. )
• Molecular-beam epitaxy of three-dimensional and novel two-dimensional topological insulators (Applicant Mussler, Gregor )
• New Topological Insulators based on ternary chalcogenides of Bi, Pb and TI (Applicants Grin, Juri ;  Pfitzner, Arno )
• Novel 2D Materials: Functionalized Stanene and Bismuthene Honeycomb Lattices (Applicant Schäfer, Jörg )
• Optimizing interfaces between topological insulators and superconductors: Towards a local detection of Majorana states (Applicant Morgenstern, Markus )
• Probing predicted topological surface states of correlated transitionmetal oxides (Applicants Gegenwart, Philipp ;  Wenderoth, Martin )
• Proximity effects in topological insulators (Applicant Fabian, Jaroslav )
• Proximity-induced magnetism, electrodynamics, and impurites in topological insulators and Weyl semimetals (Applicant Eremin, Ilya )
• Quantum transport in 3D topological insulator nanostructures (Applicant Dufouleur, Ph.D., Joseph )
• Quantum transport in topological insulators (Applicant Mirlin, Alexander )
• Quasi-particle interference in surface- and bulk-doped topological insulators and Weyl semimetals (Applicants Bode, Matthias ;  Sessi, Paolo )
• Scanning tunneling microscopy and spectroscopy on Kondo insulators (Applicant Wirth, Steffen )
• Single crystalline Bi2Te3 und Bi2Se3 Nanowires as topological insulator materials: synthesis and properties (Applicant Toimil-Molares, Maria Eugenia )
• Spectroscopic insight into current-induced spin-transfer torques in ferromagnet/topological insulator interfaces (Applicant Plucinski, Lukasz )
• Spin- and angular - resolved ultraviolet photoemission spectroscopy of new topological insulators (Applicant Elmers, Hans-Joachim )
• Spin-Charge Locked Magneto-Transport and Mesoscopic Interference Phenomena in Topological Insulators (Applicant Richter, Klaus )
• Spin-orbit interaction in HgTe based wires (Applicant Weiss, Dieter )
• Spin-resolved STS, ARPES, and XMCD of magnetically doped topological insulator heterostructures (Applicants Hofmann, Philip ;  Wiebe, Jens )
• Spin scattering of topologically protected electrons at defects (Applicant Mavropoulos, Phivos )
• Spin transport; quantum transport; new materials; topological insulators (Applicant Beschoten, Bernd )
• Theory of optical probes of topological insulators (Applicant von Oppen, Felix )
• Thin-film hybrid structures of topological insulators with superconductors and ferromagnets: experiment and theory (Applicants Dahm, Thomas ;  Reiss, Günter )
• Thin films based on topological Heusler materials (Applicants Chadov, Stanislav ;  Felser, Claudia ;  Reiss, Günter )
• Topological Insulators in Bismuth-Halogen and Related Systems: Design, Synthesis, Optimization and Properties (Applicants Doert, Thomas ;  Isaeva, Anna )
• Topological insulators with weak and strong indices (Applicant Brouwer, Piet W. )
• Topological semimetal phases in HgTe-related alloys: Berryology and surface transport (Applicants Ernst, Arthur ;  Henk, Jürgen )
• Topological Weyl Semimetals for Spintronic Devices (Applicants Felser, Claudia ;  Parkin, Stuart )
• Transport properties of bilayer topological insulators (Applicant Trauzettel, Björn )
• Transport signatures of Majorana fermions in Coulomb blockaded topological insulator nanowires (Applicant Egger, Reinhold )
• Ultrafast carrier dynamics in topological insulators (Applicant Höfer, Ulrich )

• Spokesperson: Professor Dr. Oliver Rader