Ultrafast X-ray studies of functional materials
by Roopali Kukreja (University of California)
at ALBA Synchrotron ( Marie Curie Briefing room )
Functional materials offer a rich play ground to study electrical, magnetic, optical and mechanical properties and their interplay with each other. Their wealth of functionalities provides potential routes for energy efficient computing and information technology. Recently, ultrafast control has emerged as a fascinating avenue of manipulating these functionalities, where instead of using temperature or electric or magnetic field, ultrafast lasers can be utilized to control fundamental properties. In this talk, I will focus on time-resolved x-ray experiments to study ultrafast photoinduced strain in ferroelectric thin films and phase transitions in metal-insulator systems. I will describe our recent experimental studies using emerging synchrotron techniques and free electron laser Linac Coherent Light Source (LCLS), that can probe these materials with both high spatial and temporal resolution. In the first part of my talk, I will present ultrafast studies on photoinduced strain in ferroelectric thin film based devices with an in-situ control of the polarization state. Our time-resolved x-ray diffraction studies performed at Advanced Photon Source revealed that both magnitude and sign of strain can be controlled by the polarization state, giving a better understanding of the ultrafast photostriction mechanism in ferroelectric devices. In the second part of my talk, I will discuss temporal and spatial apping of metal-insulator (Verwey) transition in magnetite, where our time-resolved studies and x-ray photon correlation spectroscopy have shown that the phase transition proceeds via phase separation into metallic and insulating domains.