Excitonic properties of semiconducting monolayer and bilayer MoT e2

C. Robert, R. Picard, D. Lagarde, G. Wang, J. P. Echeverry, F. Cadiz, P. Renucci, A. Högele, T. Amand, X. Marie, I. C. Gerber, B. Urbaszek

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Resumen

MoTe2 belongs to the semiconducting transition-metal dichalcogenide family with certain properties differing from the other well-studied members (Mo,W)(S,Se)2. The optical band gap is in the near-infrared region, and both monolayers and bilayers may have a direct optical band gap. We first simulate the single-particle band structure of both monolayer and bilayer MoTe2 with density-functional-theory-GW calculations. We find a direct (indirect) electronic band gap for the monolayer (bilayer). By solving in addition the Bethe-Salpeter equation, we find similar energies for the direct exciton transitions in monolayers and bilayers. We then study the optical properties by means of photoluminescence (PL) excitation, reflectivity, time-resolved PL, and power-dependent PL spectroscopy. With differential reflectivity, we find a similar oscillator strength for the optical transition observed in PL in both monolayers and bilayers suggesting a direct transition in both cases. We identify the same energy for the B-exciton state in the monolayer and the bilayer. Following circularly polarized excitation, we do not find any exciton polarization for a large range of excitation energies. At low temperatures (T=10K), we measure similar PL decay times on the order of 4 ps for both monolayer and bilayer excitons with a slightly longer one for the bilayer. Finally, we observe a reduction of the exciton-exciton annihilation contribution to the nonradiative recombination in bilayers.

Idioma originalInglés
Número de artículo155425
PublicaciónPhysical Review B
Volumen94
N.º15
DOI
EstadoPublicada - 17 oct 2016
Publicado de forma externa

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Robert, C., Picard, R., Lagarde, D., Wang, G., Echeverry, J. P., Cadiz, F., Renucci, P., Högele, A., Amand, T., Marie, X., Gerber, I. C., & Urbaszek, B. (2016). Excitonic properties of semiconducting monolayer and bilayer MoT e2. Physical Review B, 94(15), [155425]. https://doi.org/10.1103/PhysRevB.94.155425