Dresden 2017 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 34: Two-dimensional materials III (joined session with TT)
HL 34.7: Hauptvortrag
Dienstag, 21. März 2017, 11:30–12:00, POT 51
Influence of dark states on excitonic spectra of transition metal dichalcogenides — •Malte Selig1,2, Dominik Christiansen1, Gunnar Berghäuser1,2, Ermin Malic2, and Andreas Knorr1 — 1Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Berlin, Germany — 2Chalmers University of Technology, Department of Physics, SE-412 96 Gothenburg, Sweden
In monolayers of transition metal dichalcogenides, excitonic effects play a significant role: Besides bright excitons, dark exciton states are formed by electrons and holes with opposite spin or constitute excitons with non-vanishing center of mass momentum well above the lightcone. Evaluating the excitonic states it turns out, that in tungsten based materials some of these dark states are energetically located below the optical accessible ones. Here, we develope excitonic Bloch equations for excitonic polarizations and densities under the influence exciton phonon interaction, adressing the strong impact of low lying dark states. We investigate the dephasing of the excitonic polarization through exciton phonon scattering [1] and the phonon mediated formation and thermalization of exciton densities. It turns out that coupling to low lying dark states is crucial for luminescence yield and lifetime. The presented results can explain several recent experimental results.
[1] M. Selig et al.,Nature Commun. 7,13279 (2016)