Degenerate topological line surface phonons in quasi-1D double helix crystal SnIP
Publication Date
2021-12-03Journal Title
npj Computational Materials
ISSN
2057-3960
Publisher
Springer Science and Business Media LLC
Volume
7
Issue
1
Language
en
Type
Article
This Version
VoR
Metadata
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Peng, B., Murakami, S., Monserrat Sanchez, B., & Zhang, T. (2021). Degenerate topological line surface phonons in quasi-1D double helix crystal SnIP. npj Computational Materials, 7 (1) https://doi.org/10.1038/s41524-021-00667-6
Abstract
<jats:title>Abstract</jats:title><jats:p>Degenerate points/lines in the band structures of crystals have become a staple of the growing number of topological materials. The bulk-boundary correspondence provides a relation between bulk topology and surface states. While line degeneracies of bulk excitations have been extensively characterised, line degeneracies of surface states are not well understood. We show that SnIP, a quasi-one-dimensional van der Waals material with a double helix crystal structure, exhibits topological nodal rings/lines in both the bulk phonon modes and their corresponding surface states. Using a combination of first-principles calculations, symmetry-based indicator theories and Zak phase analysis, we find that two neighbouring bulk nodal rings form doubly degenerate lines in their drumhead-like surface states, which are protected by the combination of time-reversal symmetry <jats:inline-formula><jats:alternatives><jats:tex-math>$${{{\mathcal{T}}}}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
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</mml:math></jats:alternatives></jats:inline-formula> and glide mirror symmetry <jats:inline-formula><jats:alternatives><jats:tex-math>$${\bar{M}}_{y}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
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</mml:math></jats:alternatives></jats:inline-formula>. Our results indicate that surface degeneracies can be generically protected by symmetries such as <jats:inline-formula><jats:alternatives><jats:tex-math>$${{{\mathcal{T}}}}{\bar{M}}_{y}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">
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</mml:math></jats:alternatives></jats:inline-formula>, and phonons provide an ideal platform to explore such degeneracies.</jats:p>
Keywords
Article, /639/301/1034/1038, /639/925/357/1016, /639/638/563, /639/766/119/2792, /639/766/119/1000/1016, article
Sponsorship
Engineering and Physical Sciences Research Council (EP/P020259/1)
Identifiers
s41524-021-00667-6, 667
External DOI: https://doi.org/10.1038/s41524-021-00667-6
This record's URL: https://www.repository.cam.ac.uk/handle/1810/331699
Rights
Licence:
http://creativecommons.org/licenses/by/4.0/
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