Ionic gating of correlated perovskite nickelates

In this work, we demonstrate that an ionic liquid gate can drive the fast motion of Li⁺ into and out of correlated perovskite nickelates such as SmNiO₃ and NdNiO₃. This modulation effect can successfully engineer the phase of the material and tune the effective gap by nearly 3 eV. X-ray absorption spectra characterization showed that the Ni-site orbital occupancy control upon the gate modulation is the primary reason for the phase transition. Electrical transport measurements illustrated that such lithiation behavior induced the drastic change in electronic transport by several orders of magnitude and is independent of temperature. The lattice dilatation can be monitored as a function of Li⁺ doping concentration via synchrotron spectroscopy and provides structural insights during the phase transition. We will discuss hydrogen versus lithium doping of the nickelates and discuss the strain-orbital filling relationships.