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SFB 1170

C06 E

Topological phases in heavy-fermion insulators and semimetals, and the importance of time-reversal or inversion symmetry


The main directions of this project have been threefold: First, we have explored the potential of heavy fermion systems (HFS) to realize novel topological phases. HFS are of particular interest due to their exotic electronic and magnetic properties driven by the interaction of the localized electrons and the conduction electrons under the influence of crystalline symmetry and band topology. This part of the project has been based on our previous results on the famous SmB6 system, whose topological (surface) properties have been the object of close and long-lasting scrutiny. Second, and partially overlapping with the first one, a crucial part was the film epitaxy with the goal to realize interesting topological and topologically promising systems not accessible in the bulk. Such films have either been delivered within the SFB 1170 (A01, A07, e.g. magnetic topological insulators, MTI) or grown specifically within C06 (4f compounds). Third, in part motivated by the emergence of intrinsic MTI at the beginning of this funding period, we have studied MTI, both intrinsic and such doped with magnetic impurities. To this end, we have taken advantage of synergies within the SFB 1170 (A05, B01 growth; A01 photoelectron spectroscopy PES) and have combined these methods with methods of C06, namely x-ray absorption spectroscopy, XAS, and x-ray magnetic circular dichroism, XMCD). The work on this project was part of several ongoing or finished PhD thesis (see the funding subsection). In addition, three master theses and two bachelor theses focusing on research connected to C06 were finalized.