Dissociation of two-dimensional excitons in monolayer WSe2

Mathieu Massicotte (1) , Fabien Vialla (1) , Peter Schmidt (1) , Mark Lundeberg (1) , Simone Latini (2) , Sten Haastrup (2) , Mark Danovich (3) , Diana Davydovskaya (1) , Kenji Watanabe (4) , Takashi Taniguchi (4) , Vladimir Fal'Ko (3) , Kristian Thygesen (2) , Thomas Pedersen (5) , Frank Koppens (1)

1 ICFO - Institut de Ciencies Fotoniques [Castelldefels]
2 Department of Physics [Lyngby]
3 University of Manchester [Manchester]
4 NIMS - National Institute for Materials Science
5 AAU - Aalborg University [Denmark]

Two-dimensional (2D) semiconducting materials are promising building blocks for optoelectronic applications, many of which require efficient dissociation of excitons into free electrons and holes. However, the strongly bound excitons arising from the enhanced Coulomb interaction in these monolayers suppresses the creation of free carriers. Here, we identify the main exciton dissociation mechanism through timeand spectrally-resolved photocurrent measurements in a monolayer WSe2 p-n junction. We find that under static in-plane electric field, excitons dissociate at a rate corresponding to the one predicted for tunnel ionization of 2D Wannier-Mott excitons. This study is essential for understanding the photoresponse of 2D semiconductors and offers design rules for the realization of efficient photodetectors, valley-dependent optoelectronics and novel quantum coherent phases.

Domaines: Matière Condensée [cond-mat]

Mathieu Massicotte, Fabien Vialla, Peter Schmidt, Mark Lundeberg, Simone Latini, et al.. Dissociation of two-dimensional excitons in monolayer WSe2. Nature Communications, 2018, ⟨10.1038/s41467-018-03864-y⟩. ⟨hal-03690483⟩