Near-field optical studies to untangle electronic ordering in complex oxides

Correlated quantum materials especially transition metal oxide thin films and bulk crystals can host intricating phase textures at the nanoscale. This includes the recently discovered moiré-type phase separations or current induced metal-insulator-metal stripes in manganites, ruthenates, and vanadium oxides. Infrared (~10-10³ meV) and terahertz (~1-10 meV) near-field nano-optics allows us to directly image those novel mesoscopic phases and study their low energy spectrum with 10 nm spatial resolution. To quantitatively resolve the phase properties, we introduced machine learning methods to predict the optical dielectric functions directly from raw imaging and spectroscopy data. Via a combination of the state-of-the-art broadband infrared light sources, improved capabilities in the scanning probe techniques, and new types of data analysis and acquisition toolboxes, we set the stage for future nanoscopic investigations of low energy electron, phonon, and spin dynamics in complex oxides systems.