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

TL;DR

This study investigates the infrared optical conductivity of a layered cobalt oxide, revealing a temperature-scaled low energy mode indicative of non-Fermi liquid behavior linked to quantum criticality.

Contribution

It demonstrates a universal /T scaling of an unconventional low energy mode in a strongly correlated cobalt oxide, highlighting quantum criticality effects.

Findings

Observation of a temperature-dependent spectral weight transfer

Identification of a low energy mode scaling with /T

Implication of non-Fermi liquid excitations from quantum criticality

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.