Welcome to the Department of Topological Quantum Chemistry

Our tool box: the periodic table
The main research areas of the Topological Quantum group are related to the design, synthesis, and investigation of new quantum materials with topological properties (1,2) and Heusler compounds (3, 4, 5). We use design rules that enable the finding of materials with properties on demand. Based on the structural and electronic structure relation between semiconductors such as GaAs or HgTe it is possible to design new topological insulators within the class of Heusler compounds XYZ with C1b structure type, semiconductors with additional properties such as superconductivity or magnetism (6). This allows eventually the realization of Majorana fermions and quantum anomalous Hall effect (6). Further examples of our work in topology include: Bernevig and Felser: topological quantum chemistry (1, 2) and new Fermions (7) and the subgroup of chiral Fermions (8, 9); discovery of Weyl fermions (10), in nonmagnetic NbP and TaAs (11, 12, 13, 14) and WP2 (15, 16, 17). The axial gravitational anomaly was identified with co-workers around Gooth in NbP (18). We predicted the magnetic Weyl semimetals in Mn3Ge, Mn3Sn Co2MnGa and Co3Sn2S3 (19, 20, 21, 22) and realized by us as high quality single crystals and proven in collaboration with groups from Princeton, Weizmann and Oxford in Mn3Ge (23), Co3Sn2S2 (22, 24, 25) and Co2MnGa (26, 27).
We have an elegant set of design rules for Heusler compounds (3 - 5) that allow devolopment for many applications including quantum and energy applications. Heusler compounds with X2YZ with L21 and XYZ with C1b structure type – show the same broad variety of properties comparable to the perovskites, including topological insulators (6), Kondo behavior, non-centrosymmetric superconductivity and conventional, tunable magnetic properties (28), non-collinear magnetism (29, 23), semiconductivity, magnetoresistance effects,  Li-ion-conductivity and other physical properties. Examples are the semiconducting Half Heusler compounds for thermoelectric applications (4) and the ferrimagnetic  Mn2YZ Heusler compounds for Skyrmions (30) and spintronic applications (31, 5, 23). These concepts can be transferred to other families of materials such as perovskites and skutterudites.



During an MPG delegation's trip to Asia, Patrick Cramer hands over the certificate of appointment as head of a Max Planck Partner Group at the MPI CPfS to Satya Guin.

When the music changes, so does the dance: Controlling cooperative electronic states in kagome metals. This is the title of the press release from the MPI for the Structure and Dynamics of Matter (MPSD) on a paper published in Nature in February ...

Congratulations to Sushmita Chandra, Xialong Feng und Ning Mao, who have all been awarded Humboldt Postdoctoral Research Fellowships in the Topological Quantum Chemistry department!

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