Hysteresis and avalanches across the metal-insulator transition in vanadium oxides

A large body of experimental evidence collected over the past two decades clearly shows that the Mott metal-insulator transition in Vanadium oxides exhibits microscale coexistence of metallic and insulating phases, implying that it is an inhomogenous first order transition. A natural consequence of such a coexistence of the two competing phases is hysteresis in resistivity, which has also been observed. Additionally, the thermal or pressure-driven hysteresis is accompanied by multiple avalanches, whose distribution is sample and device size dependent. We address all of these effects in a single framework by constructing a simple classical lattice-gas model which can be mapped to a random 'field' Ising model. The 'field' and the exchange coupling in the RFIM are readily interpreted in terms of microscopic parameters of the materials. The approach provides a natural explanation for the finding of random field Ising universality of the Mott transition. Comparison of results from our approach to experiments on V2O3 and VO2 show that the observed thermal and pressure driven hysteresis in metal-insulator transitions may be reasonably described. The framework presented here may be extended easily to inhomogenous first order transitions in other materials such as ferroelectrics or manganites. (author)