Speaker
Description
Strong interactions can fundamentally reshape exciton transport in moiré superlattices. Here, we develop multi-physics-controlled transient optical imaging to directly visualize exciton dynamics and transport under electrical gating and excitation-density control. By tracking the spatiotemporal evolution of photoexcited excitons, we map distinct transport regimes and find that the diffusion coefficient can be tuned by more than three orders of magnitude, revealing the interplay among moiré localization, carrier filling, and exciton density. Strikingly, at a filling of exactly one exciton per moiré site, we observe a transport freeze, where excitons cease diffusing over ~70 nm despite strong dipolar repulsion that would otherwise promote their expansion. First-principles calculations reveal that long-range dipole interactions create an energy barrier that suppresses diffusion without an external energy reservoir, highlighting the cooperative nature of particle motion under strong correlations. Together, these results demonstrate how interactions and filling can govern exciton transport in moiré superlattices and provide insights into collective quantum phenomena in moiré heterostructures.