Controlling quantum matter with light offers a promising route to dynamically tune its many-body properties, ranging from band topology1,2 to superconductivity3. However, achieving such optical control for strongly correlated electron systems in the steady state has remained elusive. Here we demonstrate optical switching of the spin–valley degree of freedom of itinerant ferromagnets in twisted MoTe2 (t-MoTe2) homobilayers. This system uniquely features flat valley-contrasting Chern bands and exhibits a range of strongly correlated phases at various moiré lattice fillings, including Chern insulators and ferromagnetic metals4–7. We show that the spin–valley orientation of all of these phases can be dynamically reversed by resonantly exciting the exciton–polaron8 transitions with circularly polarized light. These findings not only provide direct evidence for non-thermal optical switching of a ferromagnetic spin state at zero magnetic field but also demonstrate the possibility of dynamical control over a topological order parameter, paving the way for optical generation of chiral edge modes and topological quantum circuits.
