Dynamics of the electrically induced insulator-to-metal transition in rare-earth nickelates

Rare-earth nickelates feature an insulator-to-metal transition (IMT) that can be electrically triggered. We study the dynamics of this electrically induced transition by comparing the time-dependent transport properties of two distinct members of the ${Re\mathrm{NiO}}_3$ family: ${\mathrm{NdNiO}}_3$ and ${\mathrm{SmNiO}}_3$. We report stark differences in the nucleation and growth of the metallic phase, which evolve more rapidly for ${\mathrm{NdNiO}}_3$. With the aid of simulations, we identify the amplitude of the resistivity change across the IMT as the key parameter controlling the switching speed. Our results are in accordance with recent experiments in the ${\mathrm{VO}}_x$ family, contributing to a unified vision of the field-induced IMT dynamics across different families of correlated oxides.

Figure 1

(a) Resistivity vs temperature for ${\mathrm{NdNiO}}_3$ (blue) and ${\mathrm{SmNiO}}_3$ (red) measured in unpatterned thin films using the van der Pauw method. (b) Scanning electron microscopy image of one of the ${\mathrm{NdNiO}}_3$ nanodevices. (c) Direct current (dc) voltage vs current characteristics in ${\mathrm{NdNiO}}_3$. (d) Threshold voltage ($V_{\mathrm{Th}}$) vs temperature for ${\mathrm{NdNiO}}_3$. (e) dc voltage vs current characteristics in ${\mathrm{SmNiO}}_3$. (f) Negative differential resistance voltage ($V_{\mathrm{NDR}}$) for ${\mathrm{SmNiO}}_3$.

Figure 2

Current vs time when voltage pulses of different amplitude are applied at $t=0$ for (a) ${\mathrm{NdNiO}}_3$ at 4.2 K (top panel) and 60 K (bottom panel), (b) ${\mathrm{SmNiO}}_3$ at 300 K. Inset to (a): Magnified plot of the first nanoseconds after the voltage is applied in ${\mathrm{NdNiO}}_3$. $T=4.2$ K. At first glance, ${\mathrm{NdNiO}}_3$ at 60 K and ${\mathrm{SmNiO}}_3$ at 300 K might look very similar, but as the time axis shows, switching is ∼10 times faster for ${\mathrm{NdNiO}}_3$.

Figure 3

Incubation time (${\tau }_{\mathrm{Inc}}$) vs pulse voltage for (a) ${\mathrm{NdNiO}}_3$ and (b) ${\mathrm{SmNiO}}_3$. Several temperatures are shown in each case. The vertical dashed lines in panel (a) correspond to the $V_{\mathrm{Th}}$ plotted in Fig. 1.

Figure 4

(a) Schematic representation of current focusing in an inhomogeneous system with an insulator-to-metal transition (IMT) of magnitude ${\rho }_{\mathrm{Ins}}/{\rho }_{\mathrm{Met}}$. Current is focused into smaller areas when the ${\rho }_{\mathrm{Ins}}/{\rho }_{\mathrm{Met}}$ ratio is large. (b) Two-dimensional (2D) plots of the resistivity (left columns) and temperature (right columns) distributions obtained with resistor network simulations at the moment in which percolation takes place. Resistivity is color-coded in a logarithmic scale, while temperature is color-coded in linear scale. Note that the resistivity scale is the same for all plots, but the temperature is different for each panel to better appreciate the individual details in each case. Three different base temperatures are shown: 0.18 $T_{\mathrm{IMT}}$ (top row), 0.35 $T_{\mathrm{IMT}}$ (middle row), and 0.88 $T_{\mathrm{IMT}}$ (bottom row). $T_{\mathrm{IMT}}$ is the IMT transition temperature. The ${\rho }_{\mathrm{Ins}}/{\rho }_{\mathrm{Met}}$ ratio is ${10}^2$ (larger and smaller ratios can be seen in the Supplemental Material [43]).