EAGER: Probing High-Frequency Dynamics of Individual Domain Walls in Ferroelectrics

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Non-technical Abstract:Ferroelectrics, the electric counterpart of magnets, are usually self-divided into many domains. The boundaries separating different domains, known as the domain walls, may vibrate and absorb microwave power in ferroelectric-based devices. To date, very little is known about the high-frequency motion of individual ferroelectric domain walls due to various technical challenges. Using a special microscope, the research team aims to visualize the domain walls by their ability to absorb the electromagnetic energy. The knowledge obtained by this research is crucial for future electronic applications of these materials. An integrated research and education program at University of Texas at Austin is established such that graduate and undergraduate students are trained to explore fundamental material physics and master advanced microscopy techniques.Technical Abstract: Ferroelectric domain walls with widths of several nanometers usually exhibit properties distinct from that of the domains, which may dominate the electrodynamic responses of the entire system. For instance, it is believed that the walls, rather than the domains, play the key role in the high-frequency dielectric dispersion. Due to the lack of sensitivity in commercial impedance analyzers, however, it has been difficult to separate the contributions of domains and domain walls from conventional bulk measurements. Using a novel broadband impedance microscopy with nanoscale resolutions, this research aims to locally probe the high-frequency response of ferroelectric domain walls at variable temperatures. Both neutral and charged domain walls in proper and improper ferroelectrics are under investigation. The work is significant because it is the very first experimental study on ferroelectric dynamics down to the nanometer length scale and it helps to resolve the controversial microscopic picture of the collective domain wall vibrations. The understanding of the intrinsic dielectric dispersion of ferroelectrics in the microwave regime is also critical for their applications in communication systems. The new approach of nanoscale dielectric spectroscopy proposed in this EAGER project may lead to transformative results for modern condensed matter physics research.