Two-Dimensional\nExciton Oriented Diffusion via Periodic\nPotentials

Excitonic devices operate based on excitons, which can\nbe excited\nby photons as well as emitting photons and serve as a medium for photon-carrier\nconversion. Excitonic devices are expected to combine the advantages\nof both the high response rate of photonic devices and the high integration\nof electronic devices simultaneously. However, because of the neutral\nfeature, exciton transport is generally achieved via diffusion rather\nthan using electric fields, and the efficient control of exciton flux\ndirectionality has always been difficult. In this work, a precisely\ndesigned one-dimensional periodic nanostructure (1DPS) is used to\nintroduce periodic strain field along with resonant mode to the WS<sub>2</sub> monolayer, achieving exciton oriented diffusion with a 7.6-fold\nexciton diffusion coefficient enhancement relative to that of intrinsic,\nwhile enhancing the excitonic emission intensity by a factor of 10\nand reducing exciton saturation threshold power by 2 orders of magnitude.\nBased on the analysis of the density functional theory (DFT) and the\nfinite-element method (FEM), we attribute the anisotropy of exciton\ndiffusion to exciton funneling induced by periodic potentials, which\ndo not require excessive potential height difference for an efficient\noriented diffusion. As a result of resonant emission, the exciton\ndiffusion is dragged into the nonlinear regime owing to the high exciton\ndensity close to saturation, which improves the exciton diffusion\ncoefficient and diffusion anisotropy more appreciably.