  In stacks of transition metal dichalcogenide monolayers with arbitrary
twisting angles, we explore a new class of bright excitons arising from the
pronounced F\"{o}rster coupling, whose dimensionality is tuned by its in-plane
momentum. The low energy sector at small momenta is two-dimensional, featuring
a Mexican Hat dispersion, while the high energy sector at larger momenta
becomes three-dimensional (3D) with sizable group velocity both in-plane and
out-of-plane. By choices of the spacer thickness, interface exciton mode
strongly localized at designated layers can emerge out of the cross-dimensional
bulk dispersion for a topological origin. Step-edges in spacers can be
exploited for engineering lateral interfaces to enable interlayer communication
of the topological interface exciton. Combined with the polarization selection
rule inherited from the monolayer building block, these exotic exciton
properties open up new opportunities for multilayer design towards 3D
integration of valley exciton optoelectronics.

Mesoscale and Nanoscale Physics;Materials Science