A full gap above the Fermi level: the charge density wave of monolayer VS2

In the standard model of charge density wave (CDW) transitions, the displacement along a single phonon mode lowers the total electronic energy by creating a gap at the Fermi level, making the CDW a metal--insulator transition. Here, using scanning tunneling microscopy and spectroscopy and ab initio...

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Bibliographic Details
Published in:arXiv.org 2021-09
Main Authors: Camiel van Efferen, Berges, Jan, Hall, Joshua, Erik van Loon, Kraus, Stefan, Schobert, Arne, Wekking, Tobias, Huttmann, Felix, Plaar, Eline, Rothenbach, Nico, Ollefs, Katharina, Lucas Machado Arruda, Brookes, Nick, Schoenhoff, Gunnar, Kummer, Kurt, Wende, Heiko, Wehling, Tim, Michely, Thomas
Format: Article
Language:English
Subjects:
Anharmonicity
Antiferromagnetism
Charge density waves
Coupling
Dichroism
Electronic structure
Electrons
Fermi level
Insulators
Metal-insulator transition
Monolayers
Phonons
Scanning tunneling microscopy
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Summary:In the standard model of charge density wave (CDW) transitions, the displacement along a single phonon mode lowers the total electronic energy by creating a gap at the Fermi level, making the CDW a metal--insulator transition. Here, using scanning tunneling microscopy and spectroscopy and ab initio calculations, we show that VS\(_2\) realizes a CDW which stands out of this standard model. There is a full CDW gap residing in the unoccupied states of monolayer VS\(_2\). At the Fermi level, the CDW induces a topological metal-metal (Lifshitz) transition. Non-linear coupling of transverse and longitudinal phonons is essential for the formation of the CDW and the full gap above the Fermi level. Additionally, x-ray magnetic circular dichroism reveals the absence of net magnetization in this phase, pointing to coexisting charge and spin density waves in the ground state.
ISSN:2331-8422
DOI:10.48550/arxiv.2101.01140