Electronic structure of novel magnetic topological materials

• Applicant: Dr. Fabian Göhler
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 556350547

The revolutionary properties of novel solid quantum materials rely on various forms of strong correlation of their electron systems, among them band topology and magnetism. The combination of the latter two may provide access to utilize the application of the Quantum Anomalous Hall Effect (QAHE), provided that magnetic order can persist at technologically relevant temperatures. Materials who can inherently combine ferro- or antiferromagnetism with a non-trivial band topology are thus very promising in this regard. Recently, the successful synthesis of the first intrinsically magnetic topological insulator MnBi2Te4 has been reported, prompting further research efforts in this material class. Within this project, we will study a series of new candidates for intrinsically magnetic topological materials, namely over-stoichiometric Mn1+xSb2-xTe4 – which showed a reported record-high Curie temperature of up to 73 K – and the new compound Mn2+x(Ge, Sb)Te4, whose electronic and magnetic structure remains elusive so far. The goal of the project is to provide a comprehensive analysis of their respective electronic structure by means of advanced photoemission techniques such as soft-X-ray angle-resolved photoelectron spectroscopy (SX-ARPES), spin-resolved ARPES, and spin-filtered photoelectron momentum microscopy. This will provide the electronic properties of these materials for both the bulk and the surface, and how they evolve in the presence or absence of magnetic order. An important aspect of potential applications for new materials are inhomogeneities. By combining microscopy in both real space and momentum space, we will also study the effects of the local surface structure, such as surface termination and defects. Furthermore, we will identify the topological nature of these materials. The key signature of non-trivial band topology is a protected spin-polarized electronic surface state, which is experimentally accessible via spin-ARPES.

• DFG Programme: WBP Fellowship
• International Connection: Norway
• Host: Dr. Hendrik Bentmann