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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 . 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 . 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 . 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. . However,
chirality is also of interest for chemists , especially because of the excellent
catalytic performance of the new chiral Fermions AlPt and PdGa .
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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