#  Claudia Felser: Joint Quantum Seminar  

 



####  calendar\_today Date and Time 

 **March 13, 2019** 

 04:00PM - 06:00PM EDT 

####  pin\_drop Location 

 **Jefferson Building, Room 250**  



 

 



 

 **Prof. Claudia Felser, Max Planck Institute for Chemical Physics of Solids**

 "Topological materials science"

 Topology, a mathematical concept, recently became a hot and truly transdisciplinary topic in condensed matter physics, solid state chemistry and materials science. Since there is a direct connection between real space: atoms, valence electrons, bonds and orbitals, and reciprocal space: bands, Fermi surfaces and Berry curvature, a simple classification of topological materials in a single particle picture should be possible. One important criterion for the identification of the topological material is, in the language of chemistry, the inert pair effect of the s-electrons in heavy elements, and the symmetry of the crystal structure \[1\]. Beyond Weyl and Dirac, new fermions can be identified in compounds that have linear and quadratic 3-, 6- and 8- band crossings that are stabilized by space group symmetries \[2\]. Binary phosphides are an ideal material class for a systematic study of Dirac, Weyl and new Fermion physics, since these compounds can be grown as high-quality single crystals. A new class of topological phases that have Weyl points was also predicted in the family that includes NbP, NbAs. TaP, MoP and WP2. \[3-8\]. In magnetic materials the Berry curvature and the classical anomalous Hall (AHE) and spin Hall effect (SHE) helps to identify potentially interesting candidates. As a consequence, the magnetic Heusler compounds have already been identified as Weyl semimetals: for example, Co2YZ \[9-11\], and Co3Sn2S2\[13\]. The Anomalous Hall angle also helps to identify materials in which a QAHE should be possible in thin films. Even beyond this reciprocal Berry curvature, Heusler compounds with non-collinear magnetic structures also possess real-space topological states in the form of magnetic antiskyrmions, which have not yet been observed in other materials \[13\].

 \[1\] Bradlyn et al., Nature 547 298, (2017)

 \[2\] Bradlyn, et al., Science 353, aaf5037A (2016).

 \[3\] Shekhar, et al., Nat. Phys. 11, 645 (2015)

 \[4\] Liu, et al., Nat. Mat. 15, 27 (2016)

 \[5\] Yang, et al., Nat. Phys. 11, 728 (2015)

 \[6\] Gooth et al., Nature 547, 324 (2017)

 \[7\] Kumar, et al., Nat. Com. 8, 1642 (2017)

 \[8\] Gooth et al., Nat. Com 9 (2018) 4093

 \[9\] Kübler and Felser, EPL 114, 47005 (2016)

 \[10\] Zhijun Wang, Phys. Rev. Lett. 117, 236401 (2016)

 \[11\] Chang et al., Scientific Reports 6, 38839 (2016)

 \[12\] Liu, et al. Nat. Phys. online (2018)

 \[13\] Nayak, et al., Nature 548, 561 (2017)



 

 



 

 

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