We have performed angle-resolved photoemission spectroscopy on epitaxial films to elucidate the relationship between the fermiology and charge density waves (CDWs). We found that a two-dimensional triangular pocket in 1 monolayer (ML) is converted to a strongly warped quasi-one-dimensional (1D) Fermi surface in the 6 ML counterpart, likely associated with the -to- structural phase transition. We also revealed a metallic Fermi edge on the entire Fermi surface in 6 ML at low temperature distinct from anisotropic pseudogap in 1 ML, signifying a contrast behavior of CDW that is also supported by first-principles band-structure calculations. The present result points to the importance of simultaneously controlling the structural phase and fermiology to manipulate the CDW properties in ultrathin transition-metal dichalcogenides.
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