Imaging and harnessing electronic phase separation in nickelate thin films

Materials displaying a metal-insulator transition (MIT) have been puzzling the condensed matter community for decades, as well as offering device opportunities as electronic switches and for neuromorphic computation. One family of MIT materials are perovskite rare-earth nickelates (RNiO3) and in the case of PrNiO3 and NdNiO3 the transition is first-order, i.e. it displays a thermal hysteresis within which metallic and insulating regions coexist (phase-separation). In a recent study just published in Nano Letters, we harness this phase-separated state to achieve ultrasharp resistance switching. We measure the temperature dependence of the local resistance and the nanoscale domain distribution of NdNiO3 areas between Au contacts gapped by 40-260 nm. We find that a sharp resistance drop appears below the bulk MIT temperature at ~105 K, with an amplitude inversely scaling with the nanogap width. By using X-ray photoemission electron microscopy, we directly correlate the resistance drop with the emergence and distribution of individual metallic domains at the nanogap. Our observation provides a useful insight into percolation at the MIT of rare-earth nickelates.

This work was performed in collaboration with the Helmholtz-Zentrum Berlin.

Imaging and Harnessing Percolation at the Metal–Insulator Transition of NdNiO3 Nanogaps
Jin Hong Lee, Felix Trier, Tom Cornelissen, Daniele Preziosi, Karim Bouzehouane, Stéphane Fusil, Sergio Valencia and Manuel Bibes
Nano Lett. 19, 7801 (2019)