Anudeep Mangu1,2,Vladimir Stoica3,Hao Zheng4,Huaiyu Wang3,Quynh Nguyen2,Ramamoorthy Ramesh5,Lane Martin5,Eric Dufresne4,Haidan Wen4,John Freeland4,Long-Qing Chen3,Diling Zhu2,Venkatraman Gopalan3,Yue Cao4,Aaron Lindenberg1,2
Stanford University1,SLAC National Accelerator Laboratory2,The Pennsylvania State University3,Argonne National Laboratory4,University of California, Berkeley5
Anudeep Mangu1,2,Vladimir Stoica3,Hao Zheng4,Huaiyu Wang3,Quynh Nguyen2,Ramamoorthy Ramesh5,Lane Martin5,Eric Dufresne4,Haidan Wen4,John Freeland4,Long-Qing Chen3,Diling Zhu2,Venkatraman Gopalan3,Yue Cao4,Aaron Lindenberg1,2
Stanford University1,SLAC National Accelerator Laboratory2,The Pennsylvania State University3,Argonne National Laboratory4,University of California, Berkeley5
X-ray photon correlation spectroscopy (XPCS) offers insight into materials dynamics at the mesoscale by the analysis of speckles, but has been largely limited to equilibrium or steady-state dynamics. In this work we extend XPCS by conducting experiments at the Advanced Photon Source (APS) and Linac Coherent Light Source (LCLS) on materials undergoing dynamics induced by external pumps. In this work, we describe work done on SrTiO<sub>3</sub>/PtTiO<sub>3</sub> (STO/PTO) superlattices. This material system offers a platform with a large phase space of configurations, including polar vortices, supercrystals, and skyrmions. With the high brilliance, high degree of coherence, and short pulse duration available at LCLS we observed novel time scales emerging from mesoscale dynamics during an irreversible phase transition in SrTiO<sub>3</sub>/PtTiO<sub>3</sub> superlattices from the vortex phase to the supercrystal phase. We then conducted experiments investigating the dynamics of polar vortices and skyrmions in STO/PTO under voltage excitation. Together, these measurements reveal the spatial pinning nature during the transition and the formation and growth of domains as a function of time and voltage excitation. These experiments also revealed the effect of excess charge in the system. These measurements extend XCPS towards probing functionality in materials as it relates to mesoscale structural order.