Excitonic Complexes in n-Doped WS 2 Monolayer.

We investigate the origin of emission lines apparent in the low-temperature photoluminescence spectra of n-doped WS ₂ monolayer embedded in hexagonal BN layers using external magnetic fields and first-principles calculations. Apart from the neutral A exciton line, all observed emission lines are related to the negatively charged excitons. Consequently, we identify emissions due to both the bright (singlet and triplet) and dark (spin- and momentum-forbidden) negative trions as well as the phonon replicas of the latter optically inactive complexes. The semidark trions and negative biexcitons are distinguished. On the basis of their experimentally extracted and theoretically calculated g -factors, we identify three distinct families of emissions due to exciton complexes in WS ₂ : bright, intravalley, and intervalley dark. The g -factors of the spin-split subbands in both the conduction and valence bands are also determined.