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RESEARCH PRODUCT

Interlayer exciton dynamics in van der Waals heterostructures

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Atomically thin transition metal dichalcogenides can be stacked to van der Waals heterostructures enabling the design of new materials with tailored properties. The strong Coulomb interaction gives rise to interlayer excitons, where electrons and holes are spatially separated in different layers. In this work, we reveal the time- and momentum-dependent elementary processes behind the formation, thermalization and photoemission of interlayer excitons for the exemplary MoSe2–WSe2 heterostructure. We identify tunneling of holes from MoSe2 to WSe2 on a ps timescale as the crucial process for interlayer exciton formation. We also predict a drastic reduction of the formation time as a function of the interlayer energy offset suggesting that interlayer excitons can be externally tuned. Finally, we explain the experimental observation of a dominant photoluminescence from interlayer excitons despite the vanishingly small oscillator strength as a consequence of huge interlayer exciton occupations at low temperatures. Single layers of transition metal dichalcogenides are expected to be suitable for a number of applications and by stacking layers of different materials on top of each other (heterostructures) an even richer variety of properties can be explored. To this end the authors theoretically investigate cross material exciton states in a heterostructures of MoSe2 and WSe2 layers.