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CAMP Seminar:Origins of bad metal conductivity and the insulator-metal transition in the rare-earth nickelates (RNiO3, R = rare earth)

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Rafael Jaramillo, Massachusetts Institute of Technology
When
28 January 2014 from 3:30 PM to 4:30 PM
Where
339 Davey Laboratory
Contact Name
Contact Phone
814-865-0343
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For most metals increasing temperature (T) or disorder quickens electron scattering. This scattering time hypothesis informs the Drude model of electronic conductivity (s). However, for so-called bad metals with very low s this hypothesis predicts scattering times so short as to conflict with Heisenberg’s uncertainty principle. Bad metal conductivity has remained a puzzle since its discovery in the 1980s in high T superconductors.

Here we introduce the rare-earth nickelates (RNiO3, R = rare earth) as a class of bad metals. We study SmNiO3 thin films using infrared (IR) spectroscopy while varying T and disorder. We show that the interaction between lattice distortions and Ni-O bond covalence explains both the bad metal conductivity and the insulator-metal transition (IMT) in the nickelates. It does so by shifting spectral weight over the large energy scale established by the Ni-O orbital interaction, thus enabling very low s while preserving the Drude model and without violating the uncertainty principle.

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