First-principles design for strain-tunable exciton dynamics in 2D materials

Abstract: Controlling exciton motion in two-dimensional semiconductors is key to unlocking new optoelectronic and straintronic functionalities. Monolayer transition metal dichalcogenides (TMDs), with their tightly bound excitons, offer an ideal platform for such control due to their strong sensitivity to local strain. Here we present an ab initio framework for modeling exciton dynamics in inhomogeneously strained WS2, combining excitonic band structures derived from first principles with a semiclassical transport model operating in both real and momentum space. By analyzing idealized strain patterns, we reveal how excitons undergo drift, diffusion, and confinement without invoking empirical parameters. Our results uncover regimes of super-ballistic propagation and negative effective diffusion, governed entirely by the strain landscape. This work provides microscopic insight into strain-tunable exciton behavior and establishes design principles for engineering exciton flow in two-dimensional materials.