Interlayer Excitons with Large Optical Amplitudes in Layered van der Waals Materials

Research output: Research - peer-reviewJournal article – Annual report year: 2018

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Vertically stacked two-dimensional materials form an ideal platform for controlling and exploiting light-matter interactions at the nanoscale. As a unique feature, these materials host electronic excitations of both intra- and interlayer type with distinctly different properties. In this Letter, using first-principles many-body calculations, we provide a detailed picture of the most prominent excitons in bilayer MoS2, a prototypical van der Waals material. By applying an electric field perpendicular to the bilayer, we explore the evolution of the excitonic states as the band alignment is varied from perfect line-up to staggered (Type II) alignment. For moderate field strengths, the lowest exciton has intralayer character and is almost independent of the electric field. However, we find higher lying excitons that have interlayer character. They can be described as linear combinations of the intralayer B exciton and optically dark charge transfer excitons, and interestingly, these mixed interlayer excitons have strong optical amplitude and can be easily tuned by the electric field. The first-principles results can be accurately reproduced by a simple excitonic model Hamiltonian that can be straightforwardly generalized to more complex van der Waals materials.
Original languageEnglish
JournalNano Letters
Volume18
Issue number5
Pages (from-to)2984-2989
Number of pages6
ISSN1530-6984
DOIs
StatePublished - 2018
CitationsWeb of Science® Times Cited: 3

    Research areas

  • 2D materials, Heterostructures, Interlayer excitons, Many-body perturbation theory, Optical amplitude, Optional spectra
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