Mechanism of the Resistivity Switching Induced by the Joule Heating in Crystalline NbO2

Abstract

AbstractRecently, the memristive electrical transport properties in NbO2 have attracted much attention for their promising application to neuromorphic computation. At the center of debate is whether the metal‐to‐insulator transition (MIT) originates from the structural distortion (Peierls) or the electron correlation (Mott). With inputs from experiments and first principles calculations, a thermodynamical model is developed rooted in the scenario of the MIT driven by a 2nd order Peierls instability. It is found that the temperature dependence of the electrical conductivity can be accurately fit by the band gap varying with temperature due to the gradual weakening of the Nb‐Nb dimers. The resistivity switching can consequently be understood by dimer‐free metallic domains induced by local Joule heating. In solving the heat equation, it is found that the steady state cannot be reached if the applied voltage exceeds a threshold, resulting in the chaotic behavior observed in the high voltage and current states. With the Ginzburg–Landau theory and the Joule heating equation, the evolution of the metallic domains under bias voltage can be simulated and directly verified by experiments.