Sonderforschungsbereich SFB 1170 ToCoTronics

The Sonderforschungsbereich “Topological and Correlated Electronics at Surfaces and Interfaces” (ToCoTronics) aims at combining two of the most active and exciting fields of modern condensed matter physics: topological phases of matter and strong electronic correlations. In recent years, the two fields themselves have developed to an advanced level with a deep understanding of the under- lying physics. However, the combination of the two fields, in particular, the emergent physics due to the presence of both spin orbit interaction (the basis of topological phases of matter) and strong electronic correlations, is still in its infancy. Within the next 12 years, the research at ToCoTronics will shed new light on the interplay of these two fundamental interactions. We are convinced that eventually we will better understand their constructive as well as destructive influence on each other, in existing as well as in novel materials. The major question to be investigated is: How do electronic correlations affect topological phases of matter and vice versa?
To answer this long-term question many intermediate steps have to be taken: (i) The quality of existing materials that are known to be topological insulators will be improved upon to reduce the influence of disorder on observable phenomena. (ii) These materials will be interfaced with superconductors and ferromagnets to induce novel topological phases such as topological superconductivity and the quantum anomalous Hall effect. (iii) The unique features of these systems will be functionalized, for instance, for spintronics applications. (iv) The interplay of spin-orbit coupling and Coulomb interaction will be investigated on general grounds because these are the basic ingredients for strongly corre-lated topological phases. (v) Novel topological materials with strongly interacting constituents will be predicted to engineer an electronic system where topology and interactions are equally important.
Undoubtedly, a key advantage of the Physics Department at WĂĽrzburg University is the broad base of systems and materials, as well as experimental and theoretical methods. We are in the comfortable situation to be able to investigate all of the important intermediate steps mentioned above by leading in-house experts for specific tasks. In the long run, we expect to deeply understand the interplay of Coulomb interaction and topology. We envision that this understanding will eventually lead to the prediction and realization of innovative device concepts related to spintronics applications.