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

Autor: Camiel, van Efferen, Jan, Berges, Joshua, Hall, Erik, van Loon, Stefan, Kraus, Arne, Schobert, Tobias, Wekking, Felix, Huttmann, Eline, Plaar, Nico, Rothenbach, Katharina, Ollefs, Lucas Machado, Arruda, Nick, Brookes, Gunnar, Schönhoff, Kurt, Kummer, Heiko, Wende, Tim, Wehling, Thomas, Michely
Rok vydání: 2020
Předmět:
Zdroj: Nature Communications
ISSN: 2041-1723
Popis: 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 VS2 realizes a CDW which stands out of this standard model. There is a full CDW gap residing in the unoccupied states of monolayer VS2. 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.
A charge density wave (CDW) normally creates a gap at the Fermi level, inducing a metal-insulator transition. Here, the authors report that a CDW gap resides in the unoccupied states but induces a topological metal-metal transition at the Fermi level in monolayer VS2.
Databáze: OpenAIRE