1. Nanoscale phase transitions
We are working on elucidating how phase transitions at the nanoscale differ from the bulk, the pathways underlying how they transform, and the associated time-scales, in a variety of semiconducting, superionic, phase-change, and ferroelectric nanomaterials with applications to electrochemical and information storage technologies . These measurements make use of x-ray scattering, spectroscopy and nonlinear optical techniques to visualize the first steps in these processes.
2. All-optical control of materials
We are interested in the use of light to manipulate and engineer the functionality of materials. Experiments make use of light ranging from x-rays to far infrared terahertz (THz) frequency light pulses, approaching the limit where the electric and magnetic field turn on and then turn off within a single optical cycle, and with field strengths of order the fields that hold atoms together within materials. Current work is focused on investigating mechanisms for all-optical switching in ferroelectric and multiferroic materials, and their ultrafast photovoltaic response. We are also investigating high field breakdown processes exploring the limits of material response in extreme electric and magnetic fields.
3. THz photonics
Experiments are focused on generating, manipulating, shaping, and exploring the flow of light at THz frequencies, through electron-beam-based and plasma-based sources, and through the use of nano-structured metallic field enhancement devices.
4. Femtosecond liquid phase dynamics
We use femtosecond and picosecond x-ray pulses to directly measure the structural rearrangements and making and breaking of bonds that occur in liquids associated with charge transfer reactions, intramolecular vibrational excitation, and direct excitation of hydrogen bonds, capturing the first steps in chemical reactions that occur in the liquid phase and at solid-liquid interfaces, and associated solvation dynamics. These make use of nanofluidic cells and high speed liquid jets, with the goal of directly probing the dynamical processes underlying the water splitting process as it occurs in photosynthetic and photoelectrochemical reactions, and under high pressure conditions.