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Unconventional Charge-Density-Wave Gap in Monolayer NbS2

Knispel, Timo ; Berges, Jan ; Schobert, Arne ; van Loon, Erik G. C. P. LU ; Jolie, Wouter ; Wehling, T. O. ; Michely, Thomas and Fischer, Jeison (2024) In Nano Letters 24(4). p.1045-1051
Abstract
Using scanning tunneling microscopy and spectroscopy, for a monolayer of transition metal dichalcogenide H-NbS2 grown by molecular beam epitaxy on graphene, we provide unambiguous evidence for a charge density wave (CDW) with a 3 × 3 superstructure, which is not present in bulk NbS2. Local spectroscopy displays a pronounced gap on the order of 20 meV at the Fermi level. Within the gap, low-energy features are present. The gap structure with its low-energy features is at variance with the expectation for a gap opening in the electronic band structure due to a CDW. Instead, comparison with ab initio calculations indicates that the observed gap structure must be attributed to combined electron–phonon quasiparticles. The... (More)
Using scanning tunneling microscopy and spectroscopy, for a monolayer of transition metal dichalcogenide H-NbS2 grown by molecular beam epitaxy on graphene, we provide unambiguous evidence for a charge density wave (CDW) with a 3 × 3 superstructure, which is not present in bulk NbS2. Local spectroscopy displays a pronounced gap on the order of 20 meV at the Fermi level. Within the gap, low-energy features are present. The gap structure with its low-energy features is at variance with the expectation for a gap opening in the electronic band structure due to a CDW. Instead, comparison with ab initio calculations indicates that the observed gap structure must be attributed to combined electron–phonon quasiparticles. The phonons in question are the elusive amplitude and phase collective modes of the CDW transition. Our findings advance the understanding of CDW mechanisms in 2D materials and their spectroscopic signatures. (Less)
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author
; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Nano Letters
volume
24
issue
4
pages
6 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • pmid:38232959
  • scopus:85183484204
ISSN
1530-6992
DOI
10.1021/acs.nanolett.3c02787
project
Correlated materials beyond dynamical mean-field theory
language
English
LU publication?
yes
id
b9cfffcc-0367-4ed9-a98c-6f78fcc6c6dc
date added to LUP
2024-02-01 12:13:23
date last changed
2024-02-15 10:37:26
@article{b9cfffcc-0367-4ed9-a98c-6f78fcc6c6dc,
  abstract     = {{Using scanning tunneling microscopy and spectroscopy, for a monolayer of transition metal dichalcogenide H-NbS<sub>2</sub> grown by molecular beam epitaxy on graphene, we provide unambiguous evidence for a charge density wave (CDW) with a 3 × 3 superstructure, which is not present in bulk NbS<sub>2</sub>. Local spectroscopy displays a pronounced gap on the order of 20 meV at the Fermi level. Within the gap, low-energy features are present. The gap structure with its low-energy features is at variance with the expectation for a gap opening in the electronic band structure due to a CDW. Instead, comparison with ab initio calculations indicates that the observed gap structure must be attributed to combined electron–phonon quasiparticles. The phonons in question are the elusive amplitude and phase collective modes of the CDW transition. Our findings advance the understanding of CDW mechanisms in 2D materials and their spectroscopic signatures.}},
  author       = {{Knispel, Timo and Berges, Jan and Schobert, Arne and van Loon, Erik G. C. P. and Jolie, Wouter and Wehling, T. O. and Michely, Thomas and Fischer, Jeison}},
  issn         = {{1530-6992}},
  language     = {{eng}},
  month        = {{01}},
  number       = {{4}},
  pages        = {{1045--1051}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Nano Letters}},
  title        = {{Unconventional Charge-Density-Wave Gap in Monolayer NbS<sub>2</sub>}},
  url          = {{http://dx.doi.org/10.1021/acs.nanolett.3c02787}},
  doi          = {{10.1021/acs.nanolett.3c02787}},
  volume       = {{24}},
  year         = {{2024}},
}