  We investigate the dispersive paramagnetic excitons on the honeycomb lattice
that originate from the crystalline-electric field (CEF) split localized
f-electron states in the paramagnetic state due to intersite exchange. We start
with a symmetry analysis of possible Ising-type singlet-singlet and xy-type
singlet-doublet models. The former supports only symmetric intersite-exchange
while the latter additionally allows for antisymmetric Dzyaloshinski-Moriya
(DM) exchange interactions. We calculate the closed expressions for magnetic
exciton dispersion using both response function formalism and the bosonic
Bogoliubov approach. We do this for the most general model that shows inversion
symmetry breaking on the honeycomb lattice but also discuss interesting special
cases. By calculating Berry curvatures and Chern numbers of paramagnetic
excitons we show that the xy model supports nontrivial topological states in a
wide range of parameters. This leads to the existence of excitonic topological
edge states with Dirac dispersion lying in the zone boundary gap without the
presence of magnetic order.
