Formation of monolayer charge density waves and anomalous edge doping in Na doped bulk VSe$_2$

Ulysse Chazarin (1, 2) , Mahé Lezoualc'H (3) , Jyh‐ping Chou (4) , Woei Wu Pai (2) , Abhishek Karn (2) , Raman Sankar (5) , Cyril Chacon (1) , Yann Girard (1) , Vincent Repain (1) , Amandine Bellec (1) , Sylvie Rousset (1) , Alexander Smogunov (3) , Yannick Dappe (3) , Jérôme Lagoute (1)

1 MPQ (UMR_7162) - Laboratoire Matériaux et Phénomènes Quantiques
2 NTU - National Taiwan University [Taiwan]
3 SPEC - UMR3680 - Service de physique de l'état condensé
4 NCUE - National Changhua University of Education
5 Institute of Physics, Academia Sinica

Alkali atom doping is an efficient way to induce charge transfer and Fermi level tuning in layered materials through intercalation. However, there is a general lack of microscopic understanding of the effect of doping inhomogeneity in geometric and electronic aspects. Here we report surface doping of a bulk VSe$_2$ crystal by sodium. Na atoms form intercalated subsurface islands that modify the electronic phase of the top layer of VSe2. In addition to n-doping, the charge density wave of the intercalated VSe2 surface layer changes from the ( 4×4 ) bulk phase to the ( √3 ×√7 ) known in monolayer phase of VSe$_2$. Surprisingly, an electronic state at the edges of Na-intercalated area shift anomalously upward in energy as detected by scanning tunneling spectroscopy. This is explained by a local gating effect resulting from local dipoles at the edges. Our study illustrates a clear example of intercalation effect that should be general in alkali-intercalated bulk layered materials.

Domaines: Physique [physics]; Physique [physics]

Ulysse Chazarin, Mahé Lezoualc'H, Jyh‐ping Chou, Woei Wu Pai, Abhishek Karn, et al.. Formation of monolayer charge density waves and anomalous edge doping in Na doped bulk VSe$_2$. Advanced Materials Interfaces, 2022, 10, pp.2201680. ⟨10.1002/admi.202201680⟩. ⟨cea-03938036⟩