Emergent tunability in polar vortices

Superlattice films of layers of PbTiO 3 and SrTiO3 form polar vortices under the right lattice periodicity conditions. Low frequency and terahertz experiments observed both negative permittivity and interesting collective dynamics that could lead to other emergent behavior. Gigahertz complex permittivity data could provide a new insight into polar vortices dynamics and how emergent behavior develops with periodicity, but the measurements present challenges given the anisotropic nature of these complex thin films. Here, we tested a new metrology that uses coplanar waveguides designed to be sensitive to different components of the complex permittivity tensor. We tested 12 different 100 nm thick films with periodicities with and without a SrRuO 3 bottom electrode to understand how dispersion and tunability emerge with the formation of polar vortices. Taken together, these results provide new insights into the high frequency dynamics of polar vortices and how they may lead to new devices. After summarizing this work, we will discuss other ongoing research activities at the National Institute of Standards and Technology (NIST) including several new projects funded to support the CHIPS Act (Creating Helpful Incentives to Produce Semiconductors).