ω/T scaling of the optical conductivity in strongly correlated layered cobalt oxide

Abstract

We report infrared spectroscopic properties of the strongly correlated layered cobalt oxide [BiBa${}_{0.66}$K${}_{0.36}$O${}_2$]CoO${}_2$. These measurements performed on single crystals allow us to determine the optical conductivity as a function of temperature. In addition to a large temperature dependent transfer of spectral weight, an unconventional low energy mode is found. We show that both its frequency and damping scale as the temperature itself. In fact, a basic analysis demonstrates that this mode fully scales onto a function of $\omega$/T up to room temperature. This behavior suggests low energy excitations of non-Fermi liquid type originating from quantum criticality.

5 pages, 4 figures

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• Sachdev-Ye-Kitaev Models and Beyond: A Window into Non-Fermi Liquids
• Power-Law Spectra and Asymptotic $\omega /T$ Scaling in the Orbital-Selective Mott Phase of a Three-Orbital Hubbard Model
• Critical scaling of the AC conductivity and momentum dissipation