Mechanism of the Resistivity Switching Induced by the Joule Heating in Crystalline NbO$_2$

TL;DR

This paper investigates the resistivity switching in NbO$_2$ driven by Joule heating, proposing a thermodynamical model based on a Peierls-driven metal-insulator transition, and explains the chaotic high-voltage behavior through domain evolution simulations.

Contribution

It introduces a thermodynamical model linking Joule heating to resistivity switching in NbO$_2$, emphasizing the Peierls transition mechanism and domain dynamics under bias.

Findings

Resistivity switching is due to local Joule heating inducing metallic domains.

The model accurately fits the temperature-dependent conductivity data.

High voltage leads to chaotic behavior due to inability to reach steady state.

Abstract

Recently the memristive electrical transport properties in NbO$_2$ have attracted much attention for their promising application to the neuromorphic computation. At the center of debates 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, we develop a thermodynamical model rooted in the scenario of the MIT driven by a $2^{nd}$ order Peierls instability. We find 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, we find that the steady state can not 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.