The two components of the crystallographic transition in VO2

https://escholarship.org/content/qt2xf0c3gx/qt2xf0c3gx.pdf?t=pxd659

Recent progresses on physics and applications of vanadium dioxide

An attempt has been made to illuminate the intricacies of the Mott transition as applicable to binary transition metal compounds. This has been done in the light shed by recent experimental and theoretical developments taken over a wide field. The position of Mott transition has been considered with regard to the full array of binary materials offered, and the possibilities for several new systems have been indicated. The properties of materials close to either side of the transition are discussed.

Systematics of the breakdown of Mott insulation in binary transition metal compounds

We have made a detailed temperature-dependent photoemission study of ${\mathrm{VO}}_{2}/{\mathrm{TiO}}_{2}(001)$ thin films, which show a metal-insulator transition at \ensuremath{\sim}300 K. Clean surfaces were obtained by annealing the films in an oxygen atmosphere. Spectral weight transfer between the coherent and incoherent parts accompanying the metal-insulator transition was clearly observed. We also observed a hysteretic behavior of the spectra for heating-cooling cycles. We have derived the ``bulk'' spectrum of the metallic phase and found that it has a strong incoherent part. The width of the coherent part is comparable to that given by band-structure calculation in spite of its reduced spectral weight, indicating that the momentum dependence of the self-energy is significant. This is attributed to by ferromagnetic fluctuation arising from Hund's rule coupling between different d orbitals as originally proposed by Zylbersztejn and Mott. In the insulating phase, the width of the V $3d$ band shows strong temperature dependence. We attribute this to electron-phonon interaction and have reproduced it using the independent boson model with a very large coupling constant.

A. Casalot

Papers

Proprietes physiques et structurales de la phase CrxV1−xO2

Distribution cationique dans les tungstates A+B3+(WO4)2 de type wolframite