Spectroscopy is a tool for scientists to see quantum states of materials with light. When the field strength of the light approaches the internal Coulomb force of materials, it can be used to control their electronic properties by inducing nonequilibrium quantum states. In this talk, I will discuss the potential of such intense light-matter interactions in novel two-dimensional materials, monolayer transition-metal dichalcogenides (TMDs), with special emphasis on energy state control and extreme nonlinear optics. These experiments are enabled by the development of powerful mid-infrared light sources that can efficiently access internal resonance of electron-hole states, known as excitons, while avoiding sample damage that may result from direct photoabsorption. In the first part of the talk, I will present energy state control of monolayer TMDs beyond the perturbative regime, wherein a light-dressed replica and giant blue shift of excitonic states are characterized. In the second part of the talk, I will demonstrate the unique application of artificially stacked TMDs to realize nonlinear optical processes of high-harmonic generation with enhanced efficiency. These findings demonstrate the exciting opportunities of harnessing quantum dynamics beyond perturbation in novel two-dimensional materials.
Yuki Kobayashi (Stanford PULSE Institute)