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 Universitat Berlin
Gunnar Berghäuser
Technische Universitat Berlin
A. Raja
Columbia University in the City of New York
Stanford University
P. Nagler
Universitat Regensburg
C. Schuller
Universitat Regensburg
T. F. Heinz
Stanford Linear Accelerator Center
Columbia University in the City of New York
Stanford University
T. Korn
Universitat Regensburg
A. Chernikov
Universitat Regensburg
Columbia University in the City of New York
Ermin Malic
Chalmers, Physics, Condensed Matter Theory
A. Knorr
Technische Universitat Berlin
Nature Communications
2041-1723 (ISSN)
Vol. 7 Article no 13279- 13279Graphene-Based Revolutions in ICT And Beyond (Graphene Flagship)
European Commission (FP7) (EC/FP7/604391), 2013-10-01 -- 2016-03-31.
Subject Categories (SSIF 2011)
Atom and Molecular Physics and Optics
DOI
10.1038/ncomms13279