Multi-exciton states such as biexcitons, albeit theoretically predicted, have remained challenging to identify in atomically thin transition metal dichalcogenides so far. Here, we use excitation-power, electric-field and magnetic-field dependence of photoluminescence to report direct experimental evidence of two biexciton complexes in monolayer tungsten diselenide: the neutral and the negatively charged biexciton. We demonstrate bias-controlled switching between these two states, we determine their internal structure and we resolve a fine-structure splitting of 2.5 meV for the neutral biexciton. Our results unveil multi-particle exciton complexes in transition metal dichalcogenides and offer direct routes to their deterministic control in many-body quantum phenomena.
@article{arxiv.1805.04950,
title = {Charge-tuneable biexciton complexes in monolayer WSe$_{2}$},
author = {Matteo Barbone and Alejandro R. -P. Montblanch and Dhiren M. Kara and Carmen Palacios-Berraquero and Alisson R. Cadore and Domenico De Fazio and Benjamin Pingault and Elaheh Mostaani and Han Li and Bin Chen and Kenji Watanabe and Takashi Taniguchi and Sefaattin Tongay and Gang Wang and Andrea C. Ferrari and Mete Atatüre},
journal= {arXiv preprint arXiv:1805.04950},
year = {2018}
}