Isostructural metal-insulator transition in VO 2

Separating structure and electrons in VO 2 Above 341 kelvin—not far from room temperature—bulk vanadium dioxide (VO 2 ) is a metal. But as soon as the material is cooled below 341 kelvin, VO 2 turns into an insulator and, at the same time, changes its crystal structure from rutile to monoclinic. Lee et al. studied the peculiar behavior of a heterostructure consisting of a layer of VO 2 placed underneath a layer of the same material that has a bit less oxygen. In the VO 2 layer, the structural transition occurred at a higher temperature than the metal-insulator transition. In between those two temperatures, VO 2 was a metal with a monoclinic structure—a combination that does not occur in the absence of the adjoining oxygen-poor layer. Science , this issue p. 1037