Serge Luryi and Boris Spivak
Department of Electrical and Computer Engineering, Stony Brook University, Stony Brook, NY, 11794, USA
Department of Physics, University of Washington, Seattle, WA, 98195, USA
First-order metal–insulator transitions (MITs) in crystalline materials have been known for many years1 and correspond to a transformation between states with a dielectric (semiconductor) and a metallic types of conductivity. These transitions occur under the influence of certain external parameters, such as temperature and pressure, as well as with varying material composition. Materials exhibiting these phenomena include many transition metal oxides, of which over 40 are known to possess MITs.2 3
Among the best-known MIT materials are vanadium oxides. Being able to combine with oxygen in 2-, 3-, 4-, and 5-valent states, vanadium forms a series of oxides of which at least eight exhibit MITs.4 Phase transition in V2O3 occurs at a critical temperature TC = 150 K and in VO2 at TC = 340 K, with the electrical conductivity changing by up to 10 and 5 orders of magnitude, respectively. The MIT in vanadium oxides is also accompanied by a discontinuous variation of other than electrical properties, such as optical and magnetic. Vanadium dioxide, VO2, is of particular interest for technology because its transition occurs near room temperature and furthermore its TC is tunable over a wide range by doping ...