Canalized light creates directional and switchable surface structures in vanadium dioxide

Materials with switchable nanostructured surfaces enable optical and electronic functionalities beyond those of natural materials. Here we report the creation of self-organized, re-writable, laser-induced surface structures in single-crystalline vanadium dioxide. We discover anisotropic features caused by canalized surface plasmon polaritons that can only propagate along one crystal axis. The nanostructures remain mostly single-crystalline and preserve the material's sharp metal-to-insulator transition, enabling femtosecond switching by temperature or light.