Ultrafast Structural Dynamics in Materials at Atomic to Microscale Resolution

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In the coming years, innovation in materials physics will reside in our ability to understand and control the intimate relationships between the structure of materials and their properties, both at and far from equilibrium. This goal has been recognized as a Grand Challenge for the fundamental sciences in a recent US Department of Energy (DOE) report. This requires new tools, and the PIs research program is focused on the pioneering development of instruments and methods that can provide essential missing information on complex materials, and the structure and properties of systems far from equilibrium. This research program is expected to have a broad impact across all traditional scientific disciplines (Physics, Chemistry, Biology). In particular, the proposed studies are enabled by the very recent development of RF compressed ultrafast electron diffraction in the Siwick group at McGill. The orders of magnitude enhancement in instrumentation performance that RF compression provides has defined a new state-of-the-art for UED studies, a technique that has recently provided unprecedented views of atomic-level structural dynamics for several materials and demonstrated the ability to separate dynamical contributions that come from the reorganization of lattice structure from that which comes from changes in orbital occupancy (or charge density) through an ultrafast optically induced phase transition. Combined with the state-of-the-art ultrafast broadband reflectivity also available in the Siwick lab and the new Infrastructure for Advanced Imaging in the Montreal area (based on two one-of-a-kind dynamic and ultrafast transmission electron microscopes) the PI has at his disposal a suite of advanced characterization methods is capable of interrogating time-evolving processes in materials near the level of detail that is available from the tools we use to study the equilibrium structure/properties of materials. Through this proposal the PI will apply these breakthrough tools and world world-class capabilities to measure material structures and properties during transformations to study the effects of structural changes on material functionalities and the dynamics of optical excitation in materials on their nature scales of length (nm), time (fs–ps) and energy (meV) simultaneously. These tools will be employed to address a number of target problems of high impact, including (but not limited to): 1. The respective role of electron-electron correlations, orbital selection and lattice distortions in the metal-insulator transitions of a broad class of strongly correlated oxides. 2. Optically induced structural dynamics in a range of 'light active' organic crystals from azobenzenes and charge transfer salts to protien crystals.