  The energy spectra of transition metal dichalcogenides are primarily
influenced by the and orbitals. This results in a three-band model
characterized by strong spin-orbit interaction. Investigating these bands using
a projection into a two-band model is adequate for exploring electronic and
optical properties. The topological phases, spin-valley Hall effect, derived
from spin-valley Chern numbers, are also examined. The inclusion of spin-orbit
interaction breaks inversion symmetry while maintaining time-reversal symmetry.
This leads to the non-zero spin-valley dependent Hall conductivities, pivotal
for both the spin Hall and valley Hall effects. These phenomena could have
applications beyond traditional electronics, potentially encoding quantum bits.
In particular, electrons at high-symmetry points, namely the K and K' points,
might behave as if they are in a pseudospin-1 system with spin angular momentum
of and , leading to triplet energy states. Such predictions could encourage
super-Klein tunneling, which might offer insights into Majorana fermions,
relevant for topological quantum computation.
