Manipulating Interfacial Excitonic Landscapes for Exciton Transport in Two‐Dimensional Lateral Heterostructures

ABSTRACT Nanoscale energy landscapes are fundamental to low‐dimensional semiconductors, governing carrier dynamics, quantum‐state formation and optoelectronic responses. In two‐dimensional transition‐metal dichalcogenides, excitonic states are sensitive to local dielectric and compositional variations, making energy landscapes a powerful means to control quasiparticle transport. Lateral epitaxial heterostructures provide a growth‐defined route to embed one‐dimensional excitonic landscapes within a continuous monolayer. However, these interfaces are often treated as passive boundaries, and how their width and abruptness determine excitonic landscapes and intralayer transport dynamics remains unresolved. Here, we establish interface width as a structural handle for manipulating interfacial excitonic landscapes in monolayer lateral WS 2 –WSe 2 heterostructures. By tuning the interface from atomically sharp (<1 nm) to narrow (∼2 nm), wide (∼10 nm), and alloyed (>50 nm) regimes, we show that sharper interfaces produce stronger transport modulation. Atomically sharp interfaces enhance effective diffusivities in both cross‐interface and along‐interface directions to over 200% of pristine values, while producing a more than 10‐fold slowdown in cross‐interface propagation with an influence range exceeding 600 nm. We attribute these coupled effects to the width‐dependent interfacial excitonic landscape and built‐in field. This work transforms lateral interfaces into active excitonic landscapes, providing a versatile platform for deterministic exciton engineering and future optoelectronic devices.