Charge Density Wave State Suppresses Ferromagnetic Ordering in VSe₂ Monolayers

Ferromagnetic ordering of monolayer vanadium dichalcogenides (VSe₂ and VS₂) has been predicted by density functional theory (DFT), and suggestive experimental evidence for magnetic ordering in VSe₂ monolayers has been reported. However, such ferromagnetic ordering would be in stark contradiction to the known paramagnetic nature of the bulk VSe₂. Herein, we investigate the electronic structure of VSe₂ monolayers by angle-resolved photoemission spectroscopy (ARPES) and first-principles DFT. The ARPES measurements demonstrate the absence of spin-polarized bands for monolayers in close correspondence to nonmagnetic nature of the bulk VSe₂. We demonstrate that the stabilization of the nonmagnetic state occurs due to the appearance of a charge density wave (CDW) state in VSe₂ monolayers. In contrast to well-established 4 × 4 × 3 periodicity of the CDW in bulk VSe₂, we identify a √3 × √7 unit cell for VSe₂ monolayers from both scanning tunneling microscopy imaging and first-principles calculations. Moreover, DFT predicts that the √3 × √7 charge order state is energetically competitive with a ferromagnetic 1 × 1 state. This suggests that the experimentally observed CDW state is the nonmagnetic ground state of a perfect VSe₂ monolayer, consistent with the absence of spin-polarized bands in ARPES measurements. Therefore, monolayer VSe₂ is not an itinerant magnet.