Charge-tuneable biexciton complexes in monolayer WSe$_{2}$

Matteo Barbone, Alejandro R. -P. Montblanch, Dhiren M. Kara, Carmen Palacios-Berraquero, Alisson R. Cadore, Domenico De Fazio, Benjamin Pingault, Elaheh Mostaani, Han Li, Bin Chen, Kenji Watanabe, Takashi Taniguchi, Sefaattin Tongay, Gang Wang, Andrea C. Ferrari, Mete Atatüre

Published 2018-05-13Version 1

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.