Excitonic linewidth and coherence lifetime in monolayer transition metal dichalcogenides
Journal article, 2016
Atomically thin transition metal dichalcogenides are direct-gap semiconductors with strong light-matter and Coulomb interactions. The latter accounts for tightly bound excitons, which dominate their optical properties. Besides the optically accessible bright excitons, these systems exhibit a variety of dark excitonic states. They are not visible in the optical spectra, but can strongly influence the coherence lifetime and the linewidth of the emission from bright exciton states. Here, we investigate the microscopic origin of the excitonic coherence lifetime in two representative materials (WS2 and MoSe2) through a study combining microscopic theory with spectroscopic measurements. We show that the excitonic coherence lifetime is determined by phonon-induced intravalley scattering and intervalley scattering into dark excitonic states. In particular, in WS2, we identify exciton relaxation processes involving phonon emission into lower-lying dark states that are operative at all temperatures.
Author
M. Selig
Technische Universität Berlin
Gunnar Berghäuser
Technische Universität Berlin
A. Raja
Columbia University
Stanford University
P. Nagler
University of Regensburg
C. Schuller
University of Regensburg
T. F. Heinz
Stanford University
Columbia University
T. Korn
University of Regensburg
A. Chernikov
University of Regensburg
Columbia University
Ermin Malic
Chalmers, Physics, Condensed Matter Theory
A. Knorr
Technische Universität Berlin
Nature Communications
2041-1723 (ISSN) 20411723 (eISSN)
Vol. 7 Article no 13279- 13279Graphene-Based Revolutions in ICT And Beyond (Graphene Flagship)
European Commission (EC) (EC/FP7/604391), 2013-10-01 -- 2016-03-31.
Subject Categories
Atom and Molecular Physics and Optics
DOI
10.1038/ncomms13279