Dark excitons in transition metal dichalcogenides
Artikel i vetenskaplig tidskrift, 2018

Monolayer transition metal dichalcogenides (TMDs) exhibit a remarkably strong Coulomb interaction that manifests in tightly bound excitons. Due to the complex electronic band structure exhibiting several spin-split valleys in the conduction and valence band, dark excitonic states can be formed. They are inaccessibly by light due to the required spin-flip and/or momentum transfer. The relative position of these dark states with respect to the optically accessible bright excitons has a crucial impact on the emission efficiency of these materials and thus on their technological potential. Based on the solution of the Wannier equation, we present the excitonic landscape of the most studied TMD materials including the spectral position of momentum- and spin-forbidden excitonic states. We show that the knowledge of the electronic dispersion does not allow to conclude about the nature of the material's band gap since excitonic effects can give rise to significant changes. Furthermore, we reveal that an exponentially reduced photoluminescence yield does not necessarily reflect a transition from a direct to a nondirect gap material, but can be ascribed in most cases to a change of the relative spectral distance between bright and dark excitonic states.

Författare

Ermin Malic

Chalmers, Fysik, Kondenserade materiens teori

Malte Selig

Technische Universität Berlin

Maja Feierabend

Chalmers, Fysik, Kondenserade materiens teori

Samuel Brem

Chalmers, Fysik, Kondenserade materiens teori

Dominik Christiansen

Technische Universität Berlin

Florian Wendler

Technische Universität Berlin

Andreas Knorr

Technische Universität Berlin

Gunnar Berghäuser

Chalmers, Fysik, Kondenserade materiens teori

Physical Review Materials

2475-9953 (ISSN)

Vol. 2 1 014002

Graphene Core1. Graphene-based disruptive technologies (Graphene Flagship)

Europeiska kommissionen (Horisont 2020), 2016-04-01 -- 2018-03-31.

Ämneskategorier

Atom- och molekylfysik och optik

Den kondenserade materiens fysik

DOI

10.1103/PhysRevMaterials.2.014002

Mer information

Senast uppdaterat

2019-01-25