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Article Dans Une Revue Nature Communications Année : 2021

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

Résumé

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.

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Dates et versions

hal-03722344 , version 1 (13-07-2022)

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Camiel van Efferen, Jan Berges, Joshua Hall, Erik van Loon, Stefan Kraus, et al.. A full gap above the Fermi level: the charge density wave of monolayer VS2. Nature Communications, 2021, 12 (1), pp.6837-1-6837-9. ⟨10.1038/s41467-021-27094-x⟩. ⟨hal-03722344⟩
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