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arXiv · 1309.7394

Origins of bad metal conductivity and the insulator-metal transition in the rare-earth nickelates

R. Jaramillo·Sieu D. Ha·D. M. Silevitch·Shriram Ramanathan
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Abstract

For most metals, increasing temperature (T) or disorder will quicken electron scattering. This hypothesis informs the Drude model of electronic conductivity. However, for so-called bad metals this predicts scattering times so short as to conflict with Heisenberg's uncertainty principle. Here we introduce the rare-earth nickelates (RNiO_3, R = rare earth) as a class of bad metals. We study SmNiO_3 thin films using infrared spectroscopy while varying T and disorder. We show that the interaction between lattice distortions and Ni-O bond covalence explains both the bad metal conduction and the insulator-metal transition in the nickelates by shifting spectral weight over the large energy scale established by the Ni-O orbital interaction, thus enabling very low σwhile preserving the Drude model and without violating the uncertainty principle.

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R. Jaramillo, Sieu D. Ha, D. M. Silevitch, Shriram Ramanathan. 2013-09-28. Origins of bad metal conductivity and the insulator-metal transition in the rare-earth nickelates. https://doi.org/10.1038/nphys2907

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