A full gap above the Fermi level: the charge density wave of monolayer VS<sub>2</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34824213.
- Also identified by DOI 10.1038/s41467-021-27094-x and PMC identifier 8617271.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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<sub>2</sub> realizes a CDW which stands out of this standard model. There is a full CDW gap residing in the unoccupied states of monolayer VS<sub>2</sub>. 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.