Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 51: 2D Materials: Session III (joint session DS/CPP/HL)

HL 51.4: Vortrag

Freitag, 16. März 2018, 10:30–10:45, H 2032

Lifetime of Valley Excitons in Monolayer Transition Metal Dichalcogenides — •Malte Selig1, Samuel Brem2, Florian Katsch1, Gunnar Berghäuser2, Ermin Malic2, and Andreas Knorr11Nichtlineare Optik und Quantenelektronik von Halbleitern, Institut für Theoretische Physik, Technische Universität Berlin, Berlin, Germany — 2Chalmers University of Technology, Department of Physics, Gothenburg, Sweden

In monolayers of transition metal dichalcogenides, weak screening leads to the formation tightly bound excitons which dominate the optical properties of these ultrathin materials. A pronounced circular dichroism leads to a spin and valley selective excitation of excitons at the corners of the hexagonal Brillouin zone. A microscopic understanding of the lifetime of such optically injected spins is of crucial interest for future technological applications. Here, based on a Heisenberg of motion formalism for excitons, we perform microscopic momentum and spin resolved computations to investigate the impact of exciton phonon coupling and intervalley exchange coupling on the valley lifetime of excitons. In our analysis, we also include recently discussed indirect dark excitons [1,2]. In the absence of low lying dark states we find valley lifetimes below 1 ps, which increases by orders of magnitude if the material is indirect.

[1] M. Selig et al., Nat. Commun. 7, 13279 (2016)

[2] M. Selig et al., arXiv:1703.03317 (2017)

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