Ultrafast Optical Reflectivity Study of Photo-Carrier Relaxation Dynamics in Perovskite Iridates

The Ruddlesden-Popper series of perovskite iridates Sr$_{n+1}$Ir$_{n}$O$_{3n+1}$ lie close to a localization-delocalization boundary, evolving from a Mott-like magnetic insulator in the single layer (n=1) compound to a paramagnetic semi-metal in the infinite layer (n=$\infty$) compound. We will discuss the insulator-to-metal transition in perovskite iridates from the point of view of time-resolved optical reflectivity measurements. This technique probes the relaxation dynamics of photo-generated carriers, which are strongly affected by the presence of a charge gap.