Cascaded emission of single photons from the biexciton in monolayered WSe 2

• Published in: Nature communications Vol. 7; p. 13409
• Main Authors: He, Yu-Ming, Iff, Oliver, Lundt, Nils, Baumann, Vasilij, Davanco, Marcelo, Srinivasan, Kartik, Höfling, Sven, Schneider, Christian
• Format: Journal Article
• Language: English
• Published: England 10.11.2016
• ISSN: 2041-1723
• DOI: 10.1038/ncomms13409

Monolayers of transition metal dichalcogenide materials emerged as a new material class to study excitonic effects in solid state, as they benefit from enormous Coulomb correlations between electrons and holes. Especially in WSe , sharp emission features have been observed at cryogenic temperatures, which act as single photon sources. Tight exciton localization has been assumed to induce an anharmonic excitation spectrum; however, the evidence of the hypothesis, namely the demonstration of a localized biexciton, is elusive. Here we unambiguously demonstrate the existence of a localized biexciton in a monolayer of WSe , which triggers an emission cascade of single photons. The biexciton is identified by its time-resolved photoluminescence, superlinearity and distinct polarization in micro-photoluminescence experiments. We evidence the cascaded nature of the emission process in a cross-correlation experiment, which yields a strong bunching behaviour. Our work paves the way to a new generation of quantum optics experiments with two-dimensional semiconductors.