Article (Scientific journals)
Interlayer and intralayer excitons in MoS2/WS2 and MoSe2/WSe2 heterobilayers
Torun, Engin; Miranda, Henrique P.C.; Molina-Sánchez, Alejandro et al.
2018In Physical Review. B, Condensed Matter, 97, p. 245427
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Keywords :
2D heterolayers; Excitons; ab-initio many body perturbation theory
Abstract :
[en] Accurately described excitonic properties of transition metal dichalcogenide heterobilayers (HBLs) are crucial to comprehend the optical response and the charge carrier dynamics of them. Excitons in multilayer systems possess an inter- or intralayer character whose spectral positions depend on their binding energy and the band alignment of the constituent single layers. In this paper, we report the electronic structure and the absorption spectra of MoS2/WS2 and MoSe2/WSe2 HBLs from first-principles calculations. We explore the spectral positions, binding energies, and the origins of inter- and intralayer excitons and compare our results with experimental observations. The absorption spectra of the systems are obtained by solving the Bethe-Salpeter equation on top of a G0W0 calculation, which corrects the independent-particle eigenvalues obtained from density-functional theory. Our calculations reveal that the lowest energy exciton in both HBLs possess an interlayer character which is decisive regarding their possible device applications. Due to the spatially separated nature of the charge carriers, the binding energy of interlayer excitons might be expected to be considerably smaller than that of intralayer ones. However, according to our calculations, the binding energy of lowest energy interlayer excitons is only ∼20% lower due to the weaker screening of the Coulomb interaction between layers of the HBLs. Therefore, it can be deduced that the spectral positions of the interlayer excitons with respect to intralayer ones are mostly determined by the band offset of the constituent single layers. By comparing oscillator strengths and thermal occupation factors, we show that in luminescence at low temperature, the interlayer exciton peak becomes dominant, while in absorption it is almost invisible.
Research center :
ULHPC - University of Luxembourg: High Performance Computing
Disciplines :
Physics
Author, co-author :
Torun, Engin ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Miranda, Henrique P.C.;  Universitè Catholique de Louvain, Belgium > Institute of Condensed Matter and Nanosciences (IMCN/NAPS) ; University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
Molina-Sánchez, Alejandro;  University of Valencia, Spain > Institute of Materials Science (ICMUV)
Wirtz, Ludger ;  University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit
External co-authors :
yes
Language :
English
Title :
Interlayer and intralayer excitons in MoS2/WS2 and MoSe2/WSe2 heterobilayers
Publication date :
June 2018
Journal title :
Physical Review. B, Condensed Matter
ISSN :
1095-3795
Publisher :
American Physical Society, New York, United States - Maryland
Volume :
97
Pages :
245427
Peer reviewed :
Peer Reviewed verified by ORBi
Focus Area :
Physics and Materials Science
FnR Project :
FNR7490149 - 20 Electric Transport And Superconductivity In Transition Metal Dichalcogenides Nanolayers, 2013 (01/02/2014-31/01/2019) - Ludger Wirtz
Funders :
FNR - Fonds National de la Recherche [LU]
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