Inhibitory self-oscillation electrical dynamics in metal-to-insulator transition switching materials

Electrical triggering of metal-insulator transitions enables mimicking of the spiking behavior of biological neurons. Applying a voltage to materials such as VO₂, NbO₂, or (RE)NiO₃ which exhibit an insulator-to-metal transition (IMT), results in an abrupt conductivity increase, resembling neuronal excitation. This electrical excitation allows driving IMT materials into a spiking oscillation regime using simple RC circuits. Here, we present a new type of self-oscillation dynamics that occurs in the opposite class of metal-to-insulator transition (MIT) materials. Applying a voltage to an MIT material leads to a strong conductivity suppression, resembling neuronal inhibition. We developed an electrothermal MIT switching model based on an RL circuit, which showed the emergence of a robust oscillatory behavior over a broad range of extrinsic parameters (voltage, temperature, inductance) and intrinsic MIT material properties. Using La_0.7Sr_0.3MnO₃ as a prototypical MIT material, we experimentally demonstrate self-oscillation dynamics in simple two-terminal switching devices. Experimental results show stable ~0.1-1 MHz electrical oscillations with minimal spike-to-spike variation, which are controllable by varying the applied dc voltage, temperature, or inductance. This work demonstrates a new type of inhibitory MIT-based artificial neuron that can complement the excitatory functionalities of IMT-based neuristors in biologically plausible neuromorphic hardware.