Mott transition in VO2 revealed by infrared spectroscopy and nano-imaging

TL;DR

This study uses infrared spectroscopy and nano-imaging to observe the Mott insulator-to-metal transition in VO2, revealing nanoscale metallic puddles and divergent quasiparticle mass, advancing understanding of correlated electron systems.

Contribution

It demonstrates a combined infrared and nano-imaging approach to directly visualize the Mott transition and nanoscale metallic regions in VO2, providing new insights into correlated insulator behavior.

Findings

Nanoscale metallic puddles appear at the transition onset.

Divergent quasiparticle mass observed in metallic regions.

Infrared techniques reveal charge dynamics in inhomogeneous systems.

Abstract

Electrons in correlated insulators are prevented from conducting by Coulomb repulsion between them. When an insulator-to-metal transition is induced in a correlated insulator by doping or heating, the resulting conducting state can be radically different from that characterized by free electrons in conventional metals. We report on the electronic properties of a prototypical correlated insulator vanadium dioxide (VO2) in which the metallic state can be induced by increasing temperature. Scanning near-field infrared microscopy allows us to directly image nano-scale metallic puddles that appear at the onset of the insulator-to-metal transition. In combination with far-field infrared spectroscopy, the data reveal the Mott transition with divergent quasiparticle mass in the metallic puddles. The experimental approach employed here sets the stage for investigations of charge dynamics on the nanoscale in other inhomogeneous correlated electron systems.