Charge-tuneable biexciton complexes in monolayer WSe2

Abstract

Monolayer transition metal dichalcogenides have strong Coulomb-mediated many-body interactions. Theoretical studies have predicted the existence of numerous multi-particle excitonic states. Two-particle excitons and three-particle trions have been identified by their optical signatures. However, more complex states such as biexcitons have been elusive due to limited spectral quality of the optical emission. Here, we report direct evidence of two biexciton complexes in monolayer tungsten diselenide: the four-particle neutral biexciton and the five-particle negatively charged biexciton. We distinguish these states by power-dependent photoluminescence and demonstrate full electrical switching between them. We determine the band states of the elementary particles comprising the biexcitons through magneto-optical spectroscopy. We also resolve a splitting of 2.5 meV for the neutral biexciton, which we attribute to the fine structure, providing reference for subsequent studies. Our results unveil the nature of multi-exciton complexes in transitionmetal dichalcogenides and offer direct routes towards deterministic control in many-body quantum phenomena.

Identifying defect-related quantum emitters in monolayer WSe2

“…3(d) shows peak intensities of the σ + and σ − detection as a function of the magnetic field. The intensity of the σ − increases with increasing the magnetic field while the σ + shows completely opposite behaviour, which is similar to the behaviour of intrinsic valley excitons in TMD monolayer [47,48]. Besides the examples in the main text, more emitters with similar properties to these types are shown in Supplementary information.…”

“…The intensity of QD3 exhibits different magnetic field dependence with different helicity, as shown in Fig. 3, which results from the thermal equilibrium-related valley property [47,48].…”

Radially polarized light beams from spin-forbidden dark excitons and trions in monolayer WSe2

“…The observed fine structure splitting of the bright negative trion confirms the high quality of our sample [31]. All measured energies agree well with previous reports on excitonic states in WSe 2 MLs encapsulated with h-BN [34,35,53,54]. Multiple broad emission lines appear at low energies but are excluded from the discussion in this work.…”

Valley phonons and exciton complexes in a monolayer semiconductor

“…S1. Monolayer WSe2 hosts a rich spectrum of excitonic species [23][24][25][26][27][28] . Several previously identified excitonic states are indicated in the figure, including the neutral bright exciton ( 0 ), bright trions ( ± ) [29][30][31][32][33] , the intravalley spinforbidden dark exciton ( 0 ) 17-20, 34 , and dark trions ( ± ) 18, 35 .…”