Recent advancements in ultrafast techniques including x-ray scattering and THz spectroscopy enable the detection of collective dynamics with unprecedented spatial, temporal, and energy resolution, shedding light on the fundamental dynamical processes in quantum materials. This talk will focus on our recent efforts to track emergent dynamical properties in polar nanostructures and at oxide surfaces. In the first example, the collective dynamics of polar vortices and skyrmions in PbTiO3/SrTiO3 superlattices were discovered by THz-field-driven ultrafast x-ray scattering [1,2], opening a new avenue for high-frequency ferroelectric and optoelectronic applications. In the second example, a surface-sensitive spintronic terahertz emission spectroscopy was developed to characterize distinct surface phonon dynamics of SrTiO3 and KTaO3 that diverge significantly from the bulk counterparts [3], which have important implications for the interfacial superconductivity and ferroelectricity. Looking into the future, the recent progress of developing multimodal, multiscale dynamical imaging platforms at large-scale facilities will be discussed [4,5].
References:
[1] Q. Li et al. "Subterahertz collective dynamics of polar vortices", Nature, 592, 376-380 (2021)
[2] H. Wang et al. "Terahertz-field activation of polar skyrons", Nature Communications, 16, 8994 (2025)
[3] Z. Chu et al. “Revealing subterahertz atomic vibrations in quantum paraelectrics by surface-sensitive spintronic terahertz spectroscopy”, Science Advances, 10, eads8601 (2024)
[4] A. Zong et al. “Direct imaging of synchronized shear oscillators in a van der Waals Antiferromagnet”, Nature, 620, 988 (2023)
[5] F. Zhou et al. “Ultrafast Nanoimaging of Spin-Mediated Shear Waves in an Acoustic Cavity”, Nano Lett 23, 10213 (2023)