Dimensional crossover of the charge density wave transition in thin exfoliated VSe2

Scanning tunneling microscopy of in-situ exfoliated VSe₂ reveals a non monotonic thickness dependence of the charge density wave (CDW) order parameter and phase transition temperature. Both parameters are extracted directly form the charge modulation amplitude imaged in STM micrographs. This study lifts the contradictions of previous experiments claiming opposite thickness dependencies of the CDW and shows thickness to be a true but non trivial tuning parameter of the electronic properties in layered materials.