Cryogenic Infrared Nano-Imaging of the Metal-Insulator Transition in V$_{2}$O$_{3}$

We report on temperature-dependent (18K-300K) near-field infrared imaging of the canonical Mott insulator V$_{2}$O$_{3}$ across its temperature-driven metal-insulator transition. This was accomplished using a home-built s-SNOM (scattering-type scanning near-field optical microscope) affording unprecedented spatial sensitivity ($\approx $20 nm) to surface optical properties with simultaneously acquired AFM topography at \textit{cryogenic temperatures}. Our V$_{2}$O$_{3}$ thin film is found to exhibit extreme nano-scale electronic heterogeneity near the Mott transition (170K) from paramagnetic metal to antiferromagnetic insulator. Through a sequence of near-field infrared images acquired across the transition, we resolve dynamic spatial correlations and competition between electronic phases, offering a direct probe of the metal/insulator fill fraction in strong agreement with macroscopic transport, magnetic susceptibility, and X-ray diffraction measurements of the same film. A statistical and tomographic analysis of our near-field images supports the interpretation of a complex 3-dimensional network of phases propagating across the Mott transition.