Regensburg 2019 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 3: Layer Properties: Electronic, Optical and Mechanical Properties

DS 3.3: Vortrag

Montag, 1. April 2019, 10:00–10:15, H39

Interlayer excitons in stacked TMDC heterostructres — •Roland Gillen and Janina Maultzsc — Department Physik, Friedirch-Alexander Universität Erlangen-Nürnberg, 91054 Erlangen

We computed the theoretical bandstructures and absorption spectra of bilayer MoSe2-WSe2 and MoS2-WSe2 heterostructures with different stacking orders by solution of the excitonic Bethe-Salpeter equation with GW quasiparticle corrections [1] and inclusion of spin-orbit-coupling. We find two spin-orbit split Rydberg series of low oscillation strength below the absorption onset of the monolayer materials, which arise from spatially indirect excitations between the K points of the hexagonal Brillouin zones of the constituent materials with a binding energy on the order of 250-300 meV. Additionally, our calculations firmly establish that the fundamental band gap of MoSe2-WSe2 heterostructures is indirect and has a distinct interlayer nature, possibly giving rise to a momentum- and spatially indirect contribution [2]. These results confirm the recent experimental observation of a doublet nature of the interlayer photoluminescence. We further show that the local stacking order leads to small variations in the hybridization between the MoSe2 and WSe2 bands and has a decisive effect on the polarization dependence of the interlayer excitonic absorption [2]. Our results motivate detailed studies of electron-phonon coupling effects and exciton dynamics in TMDC heterostructures by time-resolved optical experiments and ab initio methods.

[1] Gillen et al., IEEE JSTQE 23, 1 (2017); arXiv:1605.01972 (2016)

[2] Gillen et al., Phys. Rev. B 97, 165306 (2018)