Spatially ordered transit through a canonical Mott transition revealed by cryogenic nano-imaging

We report on temperature-dependent (24K-300K) near-field infrared (IR) 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 resolution ($\sim$ 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. A sequence of nano-IR images acquired across the transition provides a direct probe of the metal/insulator fill fraction in accord with an observed percolation-driven resistive transition. We resolve dynamic evolution of electronic phases and a crossover from long- to short-range spatial correlations. Identification of the attendant V$_{2}$O$_{3}$ structural transition by X-ray diffraction reveals an unexpected decoupling of Mott and structural transitions. Supported by nano-IR imaging of remnant metallic puddles below the Mott transition, these observation point towards a novel low-temperature metallic phase.