Ultrafast dynamics of a moire charge-ordered superlattice

The advent of two-dimensional moiré systems has revolutionized the exploration of phenomena arising from strong correlations and nontrivial band topology. Recently, a moiré superstructure formed by two coexisting charge density waves (CDWs) with slightly mismatched wavevectors has been realized. These incommensurate CDWs can collectively exhibit commensurability, resulting in the jointly commensurate CDW (JC-CDW) and establishing a new paradigm for controlling moiré potential and periodicity. Realizing such functionality requires understanding how the periodicity, coherence, and amplitude of this order respond to external perturbations - yet this remains elusive. Here, we employ multimodal time-resolved diffraction to probe light-induced dynamics of JC-CDW in EuTe₄. Our results reveal a robust locking of JC-CDW wavevector and coherence length exclusively along the CDW direction, indicating preserved moiré periodicity, which leads to the formation of previously unexplored shear topological defects. Furthermore, the amplitude of coexisting CDW orders exhibit nonmonotonic temporal evolution characterized by both enhancement and reduction, demonstrating rich evolution of moiré potential depth. This transient bidirectional controllability, tunable by adjusting photo-excitation intensity, arises from the interplay between optical quenching and phase-competition-induced enhancement. These findings not only enable reconstruction of the spatiotemporal evolution of the JC-CDW and shear topological defects, but also establish a platform for optical moiré engineering and manipulation of quantum materials through topological defect control.