The origin of sub-room temperature ferromagnetism in VSe₂ monolayer: reduced dimension and electron correlation

Recently 1T-VSe₂ has been reported as one of the first room-temperature two-dimensional ferromagnets. However, this conclusion remains elusive both theoretically and experimentally. In this presentation we apply LDA+DMFT (local density approximation plus dynamical mean-field theory) approach to study the magnetic properties of bulk and monolayer VSe₂. Our results indicate that bulk 1T-VSe₂ is a paramagnetic material as well-known but the monolayer is ferromagnetically ordered. The calculated Curie temperature is ~250K. From the detailed analysis on the electronic structure and the local spin susceptibility, we attribute the formation of local moment and the monolayer ferromagnetism to the concerted effect of quasiparticle pre-localization caused by reduced dimensionality and the electronic correlation. Further analysis shows that this ferromagnetism is vulnerable to the formation of interlayer interaction or extra charge doping, which provides the useful insight to understand the controversial experiments.