Kapitza-resistance-like exciton dynamics in atomically flat MoSe${}_2$-WSe${}_2$ lateral heterojunction

Abstract

Being able to control the neutral excitonic flux is a mandatory step for the development of future room-temperature two-dimensional excitonic devices. Semiconducting Monolayer Transition Metal Dichalcogenides (TMD-ML) with extremely robust and mobile excitons are highly attractive in this regard. However, generating an efficient and controlled exciton transport over long distances is a very challenging task. Here we demonstrate that an atomically sharp TMD-ML lateral heterostructure (MoSe${}_2$-WSe${}_2$) transforms the isotropic exciton diffusion into a unidirectional excitonic flow through the junction. Using tip-enhanced photoluminescence spectroscopy (TEPL) and a modified exciton transfer model, we show a discontinuity of the exciton density distribution on each side of the interface. We introduce the concept of exciton Kapitza resistance, by analogy with the interfacial thermal resistance referred to as Kapitza resistance. By comparing different heterostructures with or without top hexagonal boron nitride (hBN) layer, we deduce that the transport properties can be controlled, over distances far greater than the junction width, by the exciton density through near-field engineering and/or laser power density. This work provides a new approach for controlling the neutral exciton flow, which is key toward the conception of excitonic devices.

References in corpus (13)

• 2D materials and van der Waals heterostructures
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• Negative excitonic diffusion in transition metal dichalcogenides
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Cited by in corpus (5)

• Roadmap for Photonics with 2D Materials
• Electrically Controlled Interfacial Charge Transfer Induced Excitons in MoSe2-WSe2 Lateral Heterostructure
• Impact of charge transfer excitons on unidirectional exciton transport in lateral TMD heterostructures
• Two dimensional semiconductors: optical and electronic properties
• Trion Engineered Multimodal Transistors in Two dimensional Bilayer Semiconductor Lateral Heterostructures