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“Topology and Chirality"
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Date: |
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Time: |
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Thursday, 28 Oct. 2021 |
Video-Recording for any system with MP4-support
- Video.mp4 (ca. 342 Mb) |
15:15 – 16:10
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Abstract:
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)