Near-field imaging of metal insulator transitions

Scattering type scanning near-field optical spectroscopy enables us to image local variations in the optical properties of materials with nanometer scale resolution.

This provides a completely new way to investigate the electronic properties of quantum matter. In particular, it can be used to study the local changes that take place as a material undergoes a phase transition. The top left image shows the topography (height map) of a film of Vanadium dioxide (VO2). This material undergoes a metal to insulator transition around room temperature. Near-field spectroscopy provides the unique insight that this transition shows strong local variations in the transition temperatures. This can be seen in the bottom right image, where patches of insulating (blue) and metallic (red) phases form a percolating network.