Speaker
Description
Recent experiments have demonstrated the potential for ultrafast changes in the functional properties of materials upon selective optical excitation of particular phonon modes. The chemical diversity of complex oxides, and their strong lattice-properties coupling, have made them ideal test systems for new experimental approaches that exploit anharmonic phonon couplings to induce and modify magnetism, superconductivity and ferroelectricity with light. In this talk, I will describe our recent theoretical efforts exploring ultrafast optical control of the functional properties of perovskite oxides. First, I will describe the theoretical framework that we have developed, and the role of electronic structure calculations in that framework. I will then focus on an example of our framework in action: dynamical stabilization of a non-equilibrium magnetic phase in GdTiO3. Finally, I will consider how to identify materials that may exhibit a large dynamical response and present our results of a systematic exploration of intrinsic materials factors that may contribute to the nonlinear phononics response in LaAlO3. Our work highlights the importance of understanding the contributions of small structural distortions to the optical response in perovskites (in contrast with large-amplitude distortions, such as octahedral rotations), and illustrates how anharmonic mode coupling strengths may not be the most important factor in which materials exhibit large or unusual responses, as has generally been assumed.
