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

Type
Publication
Nat. Commun vol. 9,1 3604. (2018)

Abstract

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. We observe a much more gradual transition when THz frequencies are utilized as a probe, in contrast to the assumptions of a classical first-order phase transition. We discuss these results in light of dynamical mean-field theory calculations of the dimer Hubbard model recently applied to VO$$_2$$, which account for a continuous temperature dependence of the optical response of the VO$$_2$$ in the insulating state.

arXiv: 1711.05242

Dr. Óscar Nájera
Software distiller & Recovering Physicists

As scientist I studied the very small quantum world. As a hacker I distill code, because software is eating the world, and less code means less errors, less problems, more world.