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

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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

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Publication details

The article was received on 09 May 2018, accepted on 01 Aug 2018 and first published on 01 Aug 2018


Article type: Paper
DOI: 10.1039/C8NR03764G
Citation: Nanoscale, 2018, Advance Article
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    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, Advance Article , DOI: 10.1039/C8NR03764G

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