Förster valley-orbit coupling and topological lattice of hybrid moiré excitons

Abstract

Hybrid excitons in moiré superlattices of two-dimensional (2D) semiconductors inherit the electric dipole, strong moiré trapping, and stacking optical selection rules from its interlayer part, whereas the intralayer part is intended for enhancing optical coupling strength. Here, we show that electron-hole Coulomb exchange, or Förster type multipole-multipole coupling, in the intralayer component qualitatively alters the properties of moiré excitons, enabling their coherent hopping between moiré traps laterally separated over 10 nm and/or across layers, where their kinetic propagation is completely suppressed. Valley-flip hopping channels are found as significant as the valley-conserving ones, leading to rich possibilities to tailor valley-orbit-couplings and introduce non-trivial topology to the moiré exciton superlattice. In twisted MoTe2 where hybrid moiré excitons feature a symmetry protection from radiative recombination, we show that Förster valley-orbit-coupling can give rise to a rich topological phase diagram.