Microscopic origin of anomalous interlayer exciton transport in van der Waals heterostructures

Abstract

Van der Waals heterostructures constitute a platform for investigating intriguing many-body quantum phenomena. In particular, transition-metal dichalcogenide (TMD) hetero-bilayers host long-lived interlayer excitons which exhibit permanent out-of-plane dipole moments. Here, we develop a microscopic theory for interlayer exciton-exciton interactions including both the dipolar nature of interlayer excitons as well as their fermionic substructure, which gives rise to an attractive fermionic exchange. We find that these interactions contribute to a drift force resulting in highly non-linear exciton propagation at elevated densities in the MoSe${}_2$-WSe${}_2$ heterostructure. We show that the propagation can be tuned by changing the number of hBN spacers between the TMD layers or by adjusting the dielectric environment. In particular, although counter-intuitive, we reveal that interlayer excitons in free-standing samples propagate slower than excitons in hBN-encapsulated TMDs - due to an enhancement of the net Coulomb-drift with stronger environmental screening. Overall, our work contributes to a better microscopic understanding of the interlayer exciton transport in technologically promising atomically thin semiconductors.

9 pages+8 pages Supplementary Material, 7 figures

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• Exciton-exciton interactions in van der Waals heterobilayers
• Electrically tunable dipolar interactions between layer-hybridized excitons
• Non-bosonic moiré excitons
• Electrically Controlled Interfacial Charge Transfer Induced Excitons in MoSe2-WSe2 Lateral Heterostructure
• Optical Signatures of Moiré Trapped Biexcitons
• Electrically tunable layer-hybridized trions in doped WSe${}_2$ bilayers
• Two dimensional semiconductors: optical and electronic properties
• Exciton fractional Chern insulators in moiré heterostructures
• A high-$\kappa$ wide-gap layered dielectric for two-dimensional van der Waals heterostructures