Optical properties of correlated materials – Or why intelligent windows may look dirty

Abstract

Materials with strong electronic Coulomb correlations play an increasing role in modern materials applications. "Thermochromic" systems, which exhibit thermally induced changes in their optical response, provide a particularly interesting case. The optical switching associated with the metal-insulator transition of vanadium dioxide (VO 2 ), for example, has been proposed for use in numerous applications, ranging from anti-laser shields to "intelligent" windows, which selectively filter radiative heat in hot weather conditions. Are present-day electronic structure techniques able to describe, or -eventually even predict -such a kind of behavior? How far are we from materials design using correlated oxides? These are the central questions we try to address in this article. We review recent attempts of calculating optical properties of correlated materials within dynamical mean field theory, and summarize results for VO 2 obtained within a novel scheme aiming at particularly simple and efficient calculations of optical transition matrix elements within localized basis sets. Finally, by optimizing the geometry of "intelligent windows," we argue that this kind of technique can, in principle, be used to provide guidance for experiments, thus giving a rather optimistic answer to the above questions.

X-Ray Spectroscopy of Ultra-Thin Oxide/Oxide Heteroepitaxial Films: A Case Study of Single-Nanometer VO2/TiO2

“…Widely considered amongst the most suitable candidates for these technologies is vanadium dioxide [9,12,18,19]. VO 2 exhibits an abrupt and ultrafast MIT near room temperature that can be triggered by small, thermal [20,21], chemical [22], mechanical [23] and electrical [24,25] perturbations.…”

Spectroscopic analysis of phase constitution of high quality VO2 thin film prepared by facile sol-gel method

“…2 As a distinct characteristic of VO 2 material, the SMT temperature can be lowered by doping aliovalent ions such as tungsten, molybdenum or niobium, [3][4][5] by tuning stress on VO 2 . 6, 7 All of these features make VO 2 materials suitable for practical applications such as smart window, 8 electronic/optical switch device, 9, 10 uncooled microbolometer, 11 electronic oscillator, 12 memristive device, 13 thermal/chemical sensor. 14,15 At present, a large number of studies focus on the preparation of high quality VO 2 thin films, since homogeneous films show reproducible SMT characteristics with no degradation.…”

Resolving the VO2 controversy: Mott mechanism dominates the insulator-to-metal transition

“…On the other hand, the calculations showed that within the metallic rutile phase, the Coulomb interaction failed to produce a MIT for reasonable values of the interaction. More recently, the problem was reconsidered by Brito et al 19 and by Biermann et al as well 20,[23][24][25] providing a rather different scenario. Brito et al found a MIT within a second monoclinic (M 2 ) phase of VO 2 that only has half the dimerization of the standard M 1 , for the same value of the Coulomb interaction.…”