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.
Highlights
Monolayer transition metal dichalcogenides have strong Coulomb-mediated many-body interactions
Previous experimental findings[20,21,22,23,25,26] assigned neutral biexcitons a larger binding energy than trions, in contrast to theoretical predictions[29,30,31,32,33], whereas ref. 24 observed a peak in 1L-molybdenum diselenide (MoSe2) in the expected energy range, which they labelled as the neutral biexciton
We use continuous wave photoluminescence (PL) measurements at cryogenic temperature combined with electrical gating and magnetic field to identify the four-particle neutral biexciton (XX0) and the five-particle negatively charged biexciton, the quinton[29] (XX−) in 1L-tungsten diselenide (WSe2)
Summary
Monolayer transition metal dichalcogenides have strong Coulomb-mediated many-body interactions. 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 powerdependent photoluminescence and demonstrate full electrical switching between them. Contrary to the exciton[14,15] and trion[16,17] states, optical studies of biexciton complexes[18,19] in 1L-TMDs have been challenging[20,21,22,23,24,25,26]: inhomogeneous broadening[27] and defect bands[28] have limited their unambiguous identification and control. Our results demonstrate tuneable access to multi-exciton complexes in TMDs and provide new ways to study and control multi-exciton phenomena
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