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

Ashish Arora*, Thorsten Deilmann, Philipp Marauhn, Matthias Drueppel, Robert Schneider, Maciej R. Molas, Diana Vaclavkova, Steffen Michaelis de Vasconcellos, Michael Rohlfing, Marek Potemski, Rudolf Bratschitsch

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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 (X-IL) 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 X-IL is clearly separated from the intralayer exciton X1sA and has a high amplitude. In contrast, in W-based compounds, X-IL 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.
Original languageEnglish
JournalNanoscale
Volume10
Issue number33
Pages (from-to)15571-15577
Number of pages7
ISSN2040-3364
DOIs
Publication statusPublished - 2018

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