Excitonic linewidth and coherence lifetime in monolayer transition metal dichalcogenides.
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 (WS2and 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.
Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany.
Malte
M
Selig
Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany.
Gunnar
G
Berghäuser
Department of Chemistry, Columbia University, New York, New York 10027, USA.|Department of Applied Physics, Stanford University, Stanford, California 94305, USA.
Archana
A
Raja
Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany.
Philipp
P
Nagler
Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany.
Christian
C
Schüller
Department of Applied Physics, Stanford University, Stanford, California 94305, USA.|SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.|Departments of Physics and Electrical Engineering, Columbia University, New York, New York 10027, USA.
Tony F
TF
Heinz
Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany.
Tobias
T
Korn
Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany.|Departments of Physics and Electrical Engineering, Columbia University, New York, New York 10027, USA.
Alexey
A
Chernikov
Chalmers University of Technology, Department of Physics, SE-412 96 Gothenburg, Sweden.
Ermin
E
Malic
Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany.
Andreas
A
Knorr