Collective phenomena in solids can be sensitive to the dimensionality of the system; a case of special interest is ${\mathrm{VSe}}_2$, which shows a $\left(\sqrt{7}\times \sqrt{3}\right)$ charge density wave (CDW) in the single layer with threefold symmetry in the normal phase spontaneously broken, in contrast to the $\left(4\times 4\right)$ in-plane CDW in the bulk. Angle-resolved photoemission spectroscopy (ARPES) from ${\mathrm{VSe}}_2$ ranging from a single layer to the bulk reveals the evolution of the electronic structure including the Fermi surface contours and the CDW gap. At a thickness of two layers, the ARPES maps are already nearly bulklike, but the transition temperature $T_{\mathrm{C}}$ for the $\left(4\times 4\right)$ CDW is much higher than the bulk value of 110 K. These results can be understood as due to dimensional crossover of phonon instability driven by a competition of nesting vectors. In this letter, we provide key insights into the CDW mechanisms and offer a perspective in the search and control of emergent phases in quantum materials.

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• Charge density waves
• Multilayer thin films
• Transition metal dichalcogenides
• Angle-resolved photoemission spectroscopy
• Molecular beam epitaxy