  The variety of excitonic states in tungsten-based dichalcogenide monolayers
stems from unique interplay between the spin and valley degrees of freedom. One
of the exciton species is the indirect exciton (momentum or valley dark), which
is responsible to a series of resonances when the monolayer is charge neutral.
We investigate the short-range electron-hole exchange interaction of the
indirect exciton, as well as its recombination mechanism mediated by
impurities. The analysis provides thorough understanding of the energy and
polarization of the zero-phonon indirect exciton resonance in the emission
spectrum.
