Physics Colloquium

Prof. Keji Lai, UT-Austin

"Microwave Dynamics of Ferroelectric Domains and Domain Walls"

4:00pm, The John A. Wheeler Lecture Hall (RLM 4.102). Coffee and cookies will be served at 3:45pm in RLM 4.102

Abstract: Conventional dielectric spectroscopy experiments study the dynamics of ions, dipoles, atoms, and electrons in bulk materials. Using a broadband (from 1 MHz to 10 GHz) impedance microscope, we show that the low-energy dynamic response to external stimuli can now be spatially resolved down to the mesoscopic length scale. In hexagonal rare-earth manganites, the dissipation of electrical energy on certain ferroelectric domain walls (DWs) is substantially enhanced at microwave frequencies. First-principles and model calculations indicate that the effect is associated with a localized vibrational mode, i.e., the periodic DW sliding around its equilibrium position. In addition to the DW oscillation, the local electromechanical energy transduction in ferroelectric domain structures can also be visualized by the impedance microscopy. The interference-like patterns vividly demonstrate the spatial variation of surface-acoustic-wave generation, which can be understood by finite-element modeling of the energy transduction. Our work opens up a new frontier to explore various acousto-electric phenomena in complex materials and novel devices by nanoscale electromagnetic imaging.