Non-volatile multi-state electrothermal resistive switching in a strongly correlated insulator thin-film device

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 current and temperature redistribution effects that create these filaments are sustained by local Joule heating, a reduction of the bias current below a second (lower) threshold leads to the disappearance of filaments, and the device switches back into the high-resistance state. Hence, electrothermal resistive switching is usually volatile. Here, on the contrary, we report on non-volatile resistive switching in a planar $\mathrm{NdNiO}_3$ 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 vs. temperature dependence of the device. At least one hundred intermediate resistance states can be prepared, which are persistent as long as the base temperature is kept constant. Further, the switching process is non-destructive, and thermal cycling can reset the device to its pristine state.