Transition metal dichacogenides have layered structures in the bulk and exhibit various characteristics ranging from normal semiconductors to charge density waves (CDW) to magnetism.  Current fabrication techniques have made it possible to extract a single composite monolayer in the laboratory and to measure the physical properties of this truly two-dimensional system. It is also possible to vary the charge carrier density by external gating methods, adding another control parameter to the monolayer configurations.  Given these new possibilities, we have performed first-principles calculations to explore the connections among charging, lattice distortion, electronic properties, and charge density waves. In particular, we will report the results for various charge density wave systems in two dimensions and explain the mechanism of forming these phases. In addition, we have also found that substantial hole doping can give rise to a CDW-to-superconductor (SC) phase transition in VSe₂.

*In collaboration with Yang-hao Chan and Chih-Piao Chuu.