  We study theoretically the electron dynamics of transition metal
dichalcogenide quantum dots in the field of an ultrashort and ultrafast
circularly polarized optical pulse. The quantum dots have the shape of a disk
and their electron systems are described within an effective model with
infinite mass boundary conditions. Similar to transition metal dichalcogenide
monolayers, a circularly polarized pulse generates ultrafast valley
polarization of such quantum dots. The dependence of the valley polarization on
the size of the dot is sensitive to the dot material and, for different
materials, show both monotonic increase with the dot radius and nonmonotonic
behavior with a local maximum at a finite dot radius.
