From quantum criticality to enhanced thermopower in strongly correlated layered cobalt oxide

TL;DR

This study identifies a magnetic quantum critical point in a layered cobalt oxide, linking quantum critical fluctuations to enhanced thermopower, with potential implications for thermoelectric materials.

Contribution

It reveals an unconventional magnetic quantum critical point in cobalt oxide and connects quantum critical fluctuations to thermopower enhancement.

Findings

Existence of a magnetic quantum critical point in cobalt oxide.

Scaling behavior of susceptibility across temperature and magnetic field.

Quantum critical fluctuations explain the anomalous thermopower.

Abstract

We report on susceptibility measurements in the strongly correlated layered cobalt oxide [BiBa0.66K0.36O2]CoO2, which demonstrate the existence of a magnetic quantum critical point (QCP) governing the electronic properties. The investigated low frequency susceptibility displays a scaling behavior with both the temperature T and the magnetic field B ranging from the high-T non-Fermi liquid down to the low-T Fermi liquid. Whereas the inferred scaling form can be discussed within the standard framework of the quantum critical phenomena, the determined critical exponents suggest an unconventional magnetic QCP of a potentially generic type. Accordingly, these quantum critical fluctuations account for the anomalous logarithmic temperature dependence of the thermopower. This result allows us to conjecture that quantum criticality can be an efficient source of enhanced thermopower.