A mixed Weyl semimetal in a two-dimensional ferromagnetic BaCrSe₂ monolayer

Weyl semimetals (WSMs) are of significant fundamental and technological importance in topotronics. Despite the fact that numerous WSMs in three dimensions are achieved, the emergence of WSMs in two-dimensional (2D) ferromagnets remains elusive. Here, we put forward the 2D BaCrSe2 monolayer with intrinsic ferromagnetic order and full spin polarization as a specific representative of WSMs via including the magnetization direction theta into the topological analysis. Remarkably, the mixed Weyl points pinned exactly at the Fermi level, and the nonzero topological charge Q = +/- 1 is indeed achieved through a closed surface that encompasses a distinct mixed Weyl point in phase space (k(x), k(y), theta). The presented results not only advance the general understanding of WSMs in 2D ferromagnets but also put forward potential applications in topotronics.