Berlin 2018 – scientific programme

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DS: Fachverband Dünne Schichten

DS 2: 2D Materials: Session I (joint session DS/CPP/HL)

DS 2.13: Talk

Monday, March 12, 2018, 12:45–13:00, H 2032

Excitonic transitions in heterostructured Mo and W transition metal dichalcogenides from first principles — •Roland Gillen and Janina Maultzsch — Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

Novel two-dimensional materials from the group of layered transition metal dichalcogenides (TMDC) attract scientific interest for their unusual physical properties, such as their strong optical response. Two ways to tailor the electronic and optical properties are (i) the combination of different TMDCs to form lateral and stacked heterostructures and (ii) creation of alloys containing different metal or chalcogen atoms. Recent experiments have suggested long-lived interlayer excitons in stacked heterostructures, with spatial separation of electrons and holes across the layers, allowing for exploitation in solar cells.

Based on recent work [1,2], we show the theoretical absorption spectra of bilayer MoSe₂-WSe₂ and MoS₂-WSe₂ heterostructures from solution of the excitonic Bethe-Salpeter equation with GW quasiparticle corrections and inclusion of spin-orbit-coupling. In accordance with experimental observations, we find contributions related to interlayer excitons below the absorption onset of the monolayer materials. Our calculations allow us to estimate the binding energy of these electron-hole pairs to be on the order of 0.2 eV for both studied heterostructures. We will further show recent calculations of the absorption spectra of alloyed MoWS₂ materials.

[1] Gillen et al., IEEE JSTQE 23, 1 (2017), [2] Gillen et al., in preparation