Quantum engineers turn theory into physics via exciton control path

Researchers from the Okinawa Institute of Science and Technology (OIST) and Stanford University have developed a novel method for Floquet engineering by utilizing excitons instead of photons. Floquet engineering involves modifying a material’s quantum states by applying periodic external forces, typically using light to alter electron energy bands in semiconductors. However, traditional photon-based Floquet engineering requires very high light intensities and frequencies, which can damage materials and produce only short-lived effects. In contrast, excitonic Floquet engineering leverages excitons—quasiparticles formed by electron-hole pairs within the material itself—which couple more strongly to the material and require significantly lower light intensities to induce hybridization of energy bands. The team demonstrated that by exciting a semiconductor to create a dense population of excitons, they could achieve stronger and more stable Floquet effects with much less optical power. Using time- and angle-resolved photoemission spectroscopy (TR-ARPES), they observed excitonic Floquet replicas after reducing the optical