Abstract: Ultrafast optical pulses can be used to modify the properties of quantum materials on ultrafast timescales. However, the mechanism by which these properties arise is still poorly understood. In this talk, I will discuss our latest work on the use of X-ray free electron lasers to track dynamics of phase transitions on ultrafast timescales and ultra short length scales. We have revealed that disorder and heterogeneity are vital for understanding the properties of quantum materials even on elementary timescales. I will discuss how we have used ultrafast diffuse X-ray scattering to reveal the formation of polarons in quantum materials [1,2,3] and how these polarons can be manipulated to drive phase transitions with increased energy efficiency [4] and the implication for light-induced phase transitions in general. I will also briefly discuss how we can directly image light-induced phase transitions in time and space using time-resolved X-ray hyperspectral coherent imaging.

[1] Science 362, 572 – 576 (2018)
[2] Science Advances 7, eabf1386 (2021)
[3] Nature Physics 19, 215 – 220 (2023)
[4] Nature Physics 20, 970 – 975 (2024)