Shining light on transition-metal oxides: unveiling the hidden Fermi liquid.

We use low energy optical spectroscopy and first principles local density approximation plus dynamical mean field theory calculations to test the hypothesis that the anomalous transport properties of strongly correlated metals originate in the strong temperature dependence of their underlying resilient quasiparticles. We express the resistivity in terms of an effective plasma frequency ω(p)* and an effective scattering rate 1/τ(tr)*. We show that in the archetypal correlated material V₂O₃, ω(p)* increases with increasing temperature, while the plasma frequency from the partial sum rule exhibits the opposite trend. 1/τ(tr)* has a more pronounced temperature dependence than the scattering rate obtained from the extended Drude analysis. The theoretical calculations of these quantities are in quantitative agreement with experiment. We conjecture that these are robust properties of all strongly correlated metals, and test the conjecture by carrying out a similar analysis on thin film NdNiO₃ on a LaAlO₃ substrate.