Strongly correlated insulators, such as Mott or charge-transfer insulators, exhibit a strong temperature dependence in their resistivity. Consequently, self-heating effects can lead to electrothermal instabilities in planar thin-film devices of these materials. When the electrical bias current exceeds a device-specific threshold, the device can switch from a high- to a low-resistance state through the formation of metallic filaments. However, since the filaments are sustained by local Joule heating after they form, reducing the bias current below a second threshold causes them to disappear, returning the device to the high-resistance state. Hence, electrothermal resistive switching is usually volatile. Here, on the contrary, we report on nonvolatile resistive switching in a planar ${\mathrm{Nd}\mathrm{Ni}\mathrm{O}}_3$ thin-film device. By combining electrical transport measurements with optical wide-field microscopy, we provide evidence for a metallic filament that persists even after returning the bias current to zero. We attribute this effect to the pronounced hysteresis between the cooling and heating branches in the resistance versus temperature dependence of the device. At least $100$ intermediate resistance states can be prepared, which are persistent as long as the base temperature is kept constant. Further, the switching process is nondestructive, and thermal cycling can reset the device to its pristine state.

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• Metal-insulator transition
• Neuromorphic computing
• Resistive switching
• Transport phenomena
• Functional materials
• Memristors
• Strongly correlated systems
• Thin films