Filament dynamics in Mott insulators*

Resistive switching, a phenomenon in which the resistance of a device can be modified by applying an electric field, is the basis for emerging technologies such as neuromorphic computing. Volatile switching is specially promising, as it may allow for the implementation of artificial spiking neurons. This type of switching is observed in Mott insulators featuring an insulator-to-metal transition which can be triggered by applying an external voltage: the material becomes conducting if a threshold is exceeded. Such switching takes place in a filamentary fashion.
Despite intense research, it is not yet known how these filaments nucleate, grow and relax. We combine reflectivity and transport measurements to image the switching process with spatial and temporal resolution. Three Mott insulators are analyzed: VO₂, V₂O₃ and V₃O₅, finding remarkable differences in the filament expansion process. We will show how these differences provide a unique insight to identify which mechanism drives the Mott transition: Joule heating or electric field.