  Electronic and topological properties of MoS2 monolayers endowed with 3d
transition metal (TM) adatoms (V-Fe) are explored by using ab initio methods
and k.p models. Without the consideration of the Hubbard U interaction, the V,
Cr, and Fe adatoms tend to locate on the top of the Mo atoms, while the most
stable site for the Mn atom is at the hollow position of the Mo-S hexagon.
After the Hubbard U is applied, the most stable sites of all the systems become
the top of the Mo atoms. Chern insulators without band inversion are achieved
in these systems. The V and Fe adsorption systems are the best candidates to
produce the topological states. The k.p model calculations indicate that these
topological states are determined by the TM magnetism, the C3v crystal field
from the MoS2 substrate, and the TM atomic spin-orbit coupling (SOC). The
special two-meron pseudospin texture is found to contribute to the topology.
The apparent difference between the Berry curvatures for the V and Fe
adsorption systems are also explored. Our results widen the understanding to
the Chern insulators and are helpful for the applications of the MoS2
monolayers in the future electronics and spintronics.
