Abstract: 

Understanding light-matter interactions and controlling matter with light are of fundamental interest in physics and engineering. This knowledge is crucial for advancing solar energy materials and developing high-performance next-generation data storage and computing systems. 

In this talk, I will fist introduce an emerging experimental approach: ultrafast X-ray diffraction, which enables the probing of dynamic behavior of matter induced by light excitation. I will then present recent investigations that push the boundaries of ultrafast X-ray diffraction techniques. 

The first advancement involves the use of diffuse X-ray scattering, allowing for resolving light-induced local lattice deformations in matter associated with polaron formation and evolution. I will showcase the results from experiments conducted on a lead halide perovskite system, revealing evolving local strain fields over tens of picoseconds as photogenerated carriers localize.

Second, I will introduce the X-ray diffraction microscopy approach to resolve light-induced changes in matter across nano- and meso-scale heterogeneity. Specifically, I will present results on multiferroic bismuth ferrite, exhibiting stripe-ordered ferroelectric domains. I will illustrate how light can induce sub-nanosecond timescale manipulation of these domains through creation and annihilation of domain walls, visualized through a combination of microscopy and diffuse scattering. 

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**Refreshments will be served at 3:30 pm beginning in the Olin Lobby.