Exciton ionization in transition-metal dichalcogenides

10/02/2016 @ 11:00 AM – 12:00 PM Asia/Singapore Timezone
Physics Conference Room (S11-02-07)

Speaker: Thomas G. Pedersen
Affiliation: Aalborg University, Denmark
Abstract Details: In photodetectors and solar cells, optically generated excitons must be ionized to separate electrons and holes. If the excitons are strongly bound, thermal ionization is inefficient. A strong electric field, however, can greatly enhance the ionization rate. We study this process theoretically for mono- and multilayer transition-metal dichalcogenides within a modified Wannier exciton model. The effects of dimensionality and screening on the exciton binding energy are discussed. In the presence of a strong electric field, the exciton energies become complex resonances. We extract the ionization (tunnelling) rate using two complementary approaches: complex scaling and hypergeometric resummation [1]. By applying these techniques to Mo and W based compounds we compute the field- dependence of the ionization rate for both monolayer and multilayer photodetectors, thereby obtaining a fundamental limit for the photoresponse rate [2].

1. H. Mera, T.G. Pedersen, and B.K. Nikolic, Nonperturbative quantum physics from low-order perturbation theory, Phys. Rev. Lett. 115, 143001 (2015).
2. T.G. Pedersen et al. Exciton ionization in multilayer transition-metal
dichalcogenides, submitted.