Atypical exciton-phonon interactions in WS2 and WSe2 monolayers revealed by resonance Raman spectroscopy
Del Corro, Elena (Universidade Federal de Minas Gerais. Departamento de Física)
Botello-Méndez, Andrés (Université Catholique de Louvain. Institute of Condensed Matter and Nanosciences)
Gillet, Yannick (Université Catholique de Louvain. Institute of Condensed Matter and Nanosciences)
Elias, Ana Laura (Pennsylvania State University. Department of Physics)
Terrones, Humberto (Rensselaer Polytechnic Institute. Department of Physics, Applied Physics, and Astronomy)
Feng, Simin (Pennsylvania State University. Department of Physics)
Fantini, Cristiano (Universidade Federal de Minas Gerais. Departamento de Física)
Rhodes, Daniel (Florida State University. National High Magnetic Field Lab)
Pradhan, Narayan (Florida State University. National High Magnetic Field Lab)
Balicas, Luis (Florida State University. National High Magnetic Field Lab)
Gonze, Xavier (Université Catholique de Louvain. Institute of Condensed Matter and Nanosciences)
Charlier, Jean Christophe (Université Catholique de Louvain. Institute of Condensed Matter and Nanosciences)
Terrones, Mauricio (Pennsylvania State University. Department of Physics)
Pimenta, Marcos A. (Universidade Federal de Minas Gerais. Departamento de Física)

Data:	2016
Descripció:	19 p.
Resum:	Resonant Raman spectroscopy is a powerful tool for providing information about excitons and exciton-phonon coupling in two-dimensional materials. We present here resonant Raman experiments of single-layered WS and WSe using more than 25 laser lines. The Raman excitation profiles of both materials show unexpected differences. All Raman features of WS monolayers are enhanced by the first-optical excitations (with an asymmetric response for the spin-orbit related X and X excitons), whereas Raman bands of WSe are not enhanced at X energies. Such an intriguing phenomenon is addressed by DFT calculations and by solving the Bethe-Salpeter equation. These two materials are very similar. They prefer the same crystal arrangement, and their electronic structure is akin, with comparable spin-orbit coupling. However, we reveal that WS and WSe exhibit quite different exciton-phonon interactions. In this sense, we demonstrate that the interaction between X and X excitons with phonons explains the different Raman responses of WS and WSe, and the absence of Raman enhancement for the WSe modes at X energies. These results reveal unusual exciton-phonon interactions and open new avenues for understanding the two-dimensional materials physics, where weak interactions play a key role coupling different degrees of freedom (spin, optic, and electronic).
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Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Matèria:	Two-dimensional materials ; Transition metal dichalcogenides ; Resonant Raman spectroscopy ; First-principles calculations ; Exciton-phonon interaction
Publicat a:	Nano letters, Vol. 16, issue 4 (April 2016) , p. 2363-2368, ISSN 1530-6992

DOI: 10.1021/acs.nanolett.5b05096

Postprint 20 p, 652.8 KB

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