Imaging the nanoscale phase separation in vanadium dioxide thin films at terahertz frequencies

Vanadium dioxide (VO\(_2\)) is a material that undergoes an insulator–metal transition upon heating above 340 K. It remains debated as to whether this electronic transition is driven by a corresponding structural transition or by strong electron–electron correlations. Here, we use apertureless scattering near-field optical microscopy to compare nanoscale images of the transition in VO\(_2\) thin films acquired at both mid-infrared and terahertz frequencies, using a home-built terahertz near-field microscope.
By — H. T. Stinson, A. Sternbach, O Nájera, R. Jing, A. S. Mcleod, T. V. Slusar, A. Mueller, L. Anderegg, H. T. Kim, M. Rozenberg, D. N. Basov

Resolving the VO\(_2\) controversy: Mott mechanism dominates the insulator-to-metal transition

We consider a minimal model to investigate the metal-insulator transition in VO\(_2\). We adopt a Hubbard model with two orbitals per unit cell, which captures the competition between Mott and singlet-dimer localization. We solve the model within dynamical mean-field theory, characterizing in detail the metal-insulator transition and finding new features in the electronic states.
By — Ó. Nájera, M. Civelli, V. Dobrosavljević, M. J. Rozenberg