Berlin 2018 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 2: 2D Materials: Session I (joint session DS/CPP/HL)
DS 2.11: Vortrag
Montag, 12. März 2018, 12:15–12:30, H 2032
Resonance profiles of valley polarization in single-layer MoS2 and MoSe2 — •Hans Tornatzky1, Roland Gillen1,2, Anne-Marie Kaulitz1, and Janina Maultzsch1,2 — 1Institut für Festkörperphysik, TU Berlin, Germany — 2Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
Transition metal dichalcogenides (TMDCs) attract a lot of interest due to their unique properties, such as the repeatedly investigated strong photoluminescence from the direct gap in few layered samples. Furthermore, TMDCs have recently become promising materials for spin- and valleytronics as circular polarized excitation leads to the generation of electron-hole-pairs with distinct spin at either K or K* points in the Brillouin zone. However, questions remain unanswered about the mechanisms of the scattering processes.
In this talk we present photoluminescence measurements with different excitation energies on single-layer MoS2 and MoSe2 in order to examine the resonance behavior of the conservation of circular polarization in these TMDCs. We find that the circular polarization of the emitted light is conserved to 100 % in MoS2 and 84 %/79 % (A/A− peaks) in MoSe2 close to resonance. The values for MoSe2 surpass any previously reported value. However, in contrast to previous predictions, the degree of circular polarization decreases clearly at energies less than the 2 LA phonon energy above the resonance.
Our findings indicate that at least two competing processes underly the depolarization of the emission in single-layer transition metal dichalcogenides.