Strongly correlated electron system host numerous intriguing phenomena, such as the superconductor-metal-insulator transition, (anti-) ferromagnetism, ferroelectricity, multiferroelectricity, and so on, and such are arising from strong interaction among fundamental degrees of freedom in the solid, i.e., charge, spin, orbital, and lattice. Their proper understanding is important to deepen our knowledge of the nature and also for the technical usage of novel functionality. We investigate novel phenomena in strongly correlated electron systems by using optical spectroscopy exploiting the light-matter interaction, and aim at revealing the working principles and designing new functional devices.
