Ultrabroadband time-resolved spectroscopy in novel types of condensed matter

In condensed matter physics, quasi-particle correlations are crucial to understanding a material’s properties. For example, strong interaction between electrons with metal-like electron configuration produces strongly correlated insulators rather than conductors, which band theory would predict. Therefore, it is important to determine the interaction strength between different degrees of freedom, e.g., electron, phonon, and spin. Time-resolved spectroscopy is a powerful technique for observing energy transfer between quasi-particles and determining the interaction strength. Ultrashort-pulse light sources with extremely broadband spectra have extended exploration of ultrafast dynamics in various materials. Here, novel types of condensed-phase matter are presented to show how several key issues regarding these materials can be resolved by broadband ultrafast time-resolved spectroscopy.