Optically controlled topology in twisted MoTe₂

Twisted transition-metal dichalcogenide systems have emerged as powerful platforms for studying correlated electronic phenomena. Of recent interest is twisted MoTe₂ (tMoTe₂), which hosts integer and fractional Chern insulator states under hole doping. Since tMoTe₂ also retains the direct band gap of its monolayer components, it is a promising platform for exploring optical interactions with topological states. Here, we report optical control over the magnetization orientation, and thus the sign of the Chern numbers of the integer and fractional Chern insulator states in tMoTe₂ using a circularly polarized pump laser. After optically initializing a topological domain of the desired sign, we use standard optical measurements to verify the domain’s sign and demonstrate the robustness of the initialized domains. This new optical initialization protocol opens the door for in-situ optical control of topological domains and future exploration of anyon braiding assisted by light.