In the first two years, UTOPIQ has already achieved major milestones. The high-repetition-rate, polarization-tunable XUV beamline was successfully integrated with the momentum microscope, producing a completely new instrument. Building on this foundation, we demonstrated valley-selective Floquet engineering in 2D materials known as transition metal dichalcogenides (TMDCs). Experiments showed that circularly polarized light can selectively control electrons in different valleys of Floquet–Bloch bands, establishing a new approach to ultrafast valleytronics. These techniques were later extended to additional 2D materials, revealing novel light-matter interaction mechanisms that were not anticipated at the start of the project.
Taken together, the project has delivered several significant accomplishments. The development of the multimodal XUV photoemission microscope represents a major methodological advance, enabling ultrafast XUV photoemission dichroism measurements that were previously impossible. The observation of valley-polarized Floquet–Bloch states directly links Floquet engineering to quantum-geometric light–matter interactions in 2D materials. Moreover, excited-state mapping combined with linear dichroism has uncovered electronic states in topological semimetals that were previously inaccessible, and the enhancement of electron–phonon coupling in nonequilibrium conditions has been demonstrated. Beyond the laboratory, these achievements have already led to rapid dissemination through publications, conferences, and new collaborations with researchers worldwide.
