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                                                “Topology and Chirality"





  Thursday, 28 Oct. 2021

    Video-Recording for any system with MP4-support

   - Video.mp4  (ca. 342 Mb)

 15:15 – 16:10





Topology, a mathematical concept, recently became a hot and truly

transdisciplinary topic in condensed matter physics, solid state chemistry and

materials science. All 200 000 inorganic materials were recently classified into

trivial and topological materials: topological insulators, Dirac, Weyl and

nodal-line semimetals, and topological metals [1]. The direct connection between

real space: atoms, valence electrons, bonds and orbitals, and reciprocal space:

bands and Fermi surfaces allows for a simple classification of topological materials

in a single particle picture. More than 25% of all inorganic compounds host

topological bands, which opens also an infinitive play-ground for chemistry [1,2].

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 [3]. 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 (Chern numbers) of ±2 [4]. In agreement with

the chiral crystal structure two different chiral surface states are observed.

A quantized circular photogalvanic effect is theoretically possible in Weyl semimetals.

However, in the multifold fermions with opposite chiralities where Weyl points can

stay at different energies, a net topological charge can be generated. [5]. However,

chirality is also of interest for chemists [6], especially because of the excellent

catalytic performance of the new chiral Fermions AlPt and PdGa [7].

The open question is the interplay between Berry curvature, chirality, orbital moment

and surface states.


1.     Bradlyn et al., Nature  547  298, (2017), Vergniory, et al., Nature 566 480 (2019),

        Xu et al. Nature 586 (2020) 702.

2.     Nitesh Kumar, Satya N. Guin, Kaustuv Manna, Chandra Shekhar, and

        Claudia Felser, doi.org/10.1021/acs.chemrev.0c00732

3.     Bradlyn, et al., Science 353, aaf5037A (2016)

4.     Sanchez et al., Nature 567 (2019) 500, Schröter et al., Nature Physics 15 (2019) 759,

        Schröter Science 369 (2020) 179, Sessi et al, Nature Communications 11 (2020) 3507,

        Yao et al., Nature Communications 11 (2020) 2033

5.     Dylan Rees, et al., Science Advances 6 (2020) eaba0509, Congcong Le, Yang Zhang,

        Claudia Felser, Yan Sun, Physical Review B 102 (2020) 121111(R), Zhuoliang Ni,

        et al., npj Quantum Materials volume 5  (2020) 96, Zhuoliang Ni, et al.,,

        Nature Communications 12 (2021) 154

6.     B. Yan, et al., Nature Com. 6 (2015) 10167, Guowei Li and Claudia Felser,

        APL 116 (2020) 070501.

7.     Qun Yang, et al., Advanced Materials 32 (2020) 1908518, Guowei Li, to be published


Speaker today:  Claudia Felser (Max Planck Institute of Chemical Physics of Solids, Germany)


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