Excitons in MoS2/MoSe2 Van der Waals heterostructures
Paulina Plochocka a
a Laboratoire National des Champs Magnétiques Intenses, CNRS (FR)
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#Sol2D19. Two Dimensional Layered Semiconductors
Berlin, Germany, 2019 November 3rd - 8th
Organizers: Efrat Lifshitz, Cristiane Morais Smith and Doron Naveh
Invited Speaker, Paulina Plochocka, presentation 443
DOI: https://doi.org/10.29363/nanoge.ngfm.2019.443
Publication date: 18th July 2019

Recently, the stacking of atomic monolayers of TMDs has emerged as an effective way to engineer their properties. In principle, the staggered band alignment of such heterostructures should result in the formation of inter-layer excitons with long lifetimes and robust valley polarization. Since single layer TMDs suffer from very short exciton lifetimes and rapid valley depolarization, TMDs heterostructures can circumvent these drawbacks, paving the way for implementation of valleytronic and spintronic concepts. In this talk I will discuss the optical properties of excitons in MoS2/MoSe2 van der Waals heterostructure. First, I will demonstrate a long lived inter-layer exciton emission. Under circularly polarized excitation, the inter-layer exciton emission is intriguingly counter polarized; the emitted light has the opposite helicity compared to the excitation.  This surprising effect could be partially explained by the formation of the Moiré excitons in van der Waals heterostructures. To support this idea I will demonstrate splitting of the intralayer exciton and trion in a monolayer MoSe2 assembled in a heterostructure with MoS2 and encapsulated in hBN. Such a splitting, observed for the first time, is a direct consequence of the Moiré pattern formed between MoSe2 and MoS2. Secondly, I will demonstrate the results of the magneto-photoluminescence spectroscopy of interlayer excitons, which exhibits a non-trivial dependence of the valley polarization as a function of the magnetic field. The measured trends can be accounted for by considering that the valley polarization of energetic levels split by the valley Zeeman effect stems from the interplay between exchange interaction and phonon mediated intervalley scattering

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