Event

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 [1]. 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. [3-5]. 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]. Crystals of chiral topological materials CoSi, AlPt and RhSi were investigated by angle resolved photoemission and show giant unusual helicoid Fermi arcs with topological charges of ±2 [6,7]. In agreement with the chiral crystal structure two different chiral surface states are observed. A quantized photogalvanic effect was observed in RhSi [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 [12]. The Anomalous Hall angle also helps to identify materials in which a QAHE should be possible in thin films. 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].

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Short Bio for the speaker:

Claudia Felser studied chemistry and physics at the University of Cologne (Germany, completing there both her diploma in solid state chemistry (1989) and her doctorate in physical chemistry (1994). After postdoctoral fellowships at the Max Planck Institute in Stuttgart (Germany) and the CNRS in Nantes (France), she joined the University of Mainz (Germany) in 1996 becoming a full professor there in 2003. She is currently Director at the Max Planck Institute for Chemical Physics of Solids in Dresden (Germany). Her research focuses are the design and discovery of novel inorganic compounds, in particular, Heusler compounds for multiple applications and new topological quantum materials. Felser was honored as a Distinguished Lecturer of the IEEE Magnetics Society in 2011 and in 2017 she received an ERC Advanced grant. In 2019, she was awarded the APS James C. McGroddy Prize for New Materials together with Bernevig, Dai and in 2014 the Alexander M. Cruickshank Lecturer Award of the Gordon Research Conference, and received a SUR-grant Award from IBM. In 2014 she received the Tsungmin Tu Research Prize from the Ministry of Science and Technology of Taiwan, the highest academic honor granted to foreign researchers in Taiwan. She is a Fellow of the American Physical Society and the Institute of Physics, London and since 2018 a member of the Leopoldina, the German National Academy of Sciences.