Issue 33, 2018

Valley-contrasting optics of interlayer excitons in Mo- and W-based bulk transition metal dichalcogenides

Abstract

Recently, spatially indirect (“interlayer”) excitons have been discovered in bulk 2H-MoTe2. They are theoretically predicted to exist in other Mo-based transition metal dichalcogenides (TMDCs) and are expected to be present in W-based TMDCs as well. We investigate interlayer excitons (XIL) in bulk 2H-MoSe2 and 2H-WSe2 using valley-resolved magneto-reflectance spectroscopy under high magnetic fields of up to 29 T combined with ab initio GW-BSE calculations. In the experiments, we observe interlayer excitons in MoSe2, while their signature is surprisingly absent in WSe2. In the calculations, we find that interlayer excitons exist in both Mo- and W-based TMDCs. However, their energetic positions and their oscillator strengths are remarkably different. In Mo-based compounds, the interlayer exciton resonance XIL is clearly separated from the intralayer exciton X1sA and has a high amplitude. In contrast, in W-based compounds, XIL is close in energy to the intralayer A exciton X1sA and possesses a small oscillator strength, which explains its absence in the experimental data of WSe2. Our combined experimental and theoretical observations demonstrate that interlayer excitons can gain substantial oscillator strength by mixing with intralayer states and hence pave the way for exploring interlayer exciton physics in Mo-based bulk transition metal dichalcogenides.

Graphical abstract: Valley-contrasting optics of interlayer excitons in Mo- and W-based bulk transition metal dichalcogenides

Supplementary files

Article information

Article type
Paper
Submitted
09 May 2018
Accepted
01 Aug 2018
First published
01 Aug 2018

Nanoscale, 2018,10, 15571-15577

Valley-contrasting optics of interlayer excitons in Mo- and W-based bulk transition metal dichalcogenides

A. Arora, T. Deilmann, P. Marauhn, M. Drüppel, R. Schneider, M. R. Molas, D. Vaclavkova, S. Michaelis de Vasconcellos, M. Rohlfing, M. Potemski and R. Bratschitsch, Nanoscale, 2018, 10, 15571 DOI: 10.1039/C8NR03764G

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