Mass-Enhanced Fermi Liquid Ground State in Na$_{1.5}$Co$_2$O$_4$

TL;DR

This study reveals a mass-enhanced Fermi liquid ground state in Na$_{1.5}$Co$_2$O$_4$, characterized by metallic resistivity, specific heat, and magnetic susceptibility behaviors indicative of heavy fermion-like properties.

Contribution

It demonstrates the existence of a heavy fermion-like Fermi liquid state in a layered oxide without magnetic order, expanding understanding of correlated electron systems.

Findings

Resistivity shows T^2 behavior below 30-40 K

Magnetic susceptibility peaks around 14 K

Electronic specific heat coefficient is approximately 60 mJ/molK^2 at 2 K

Abstract

Magnetic, transport, and specific heat measurements have been performed on layered metallic oxide Na$_{1.5}$Co$_2$O$_4$ as a function of temperature $T$. Below a characteristic temperature $T^*$=30$-$40 K, electrical resistivity shows a metallic conductivity with a $T^2$ behavior and magnetic susceptibility deviates from the Curie-Weiss behavior showing a broad peak at $\sim$14 K. The electronic specific heat coefficient $\gamma$ is $\sim$60 mJ/molK$^2$ at 2 K. No evidence for magnetic ordering is found. These behaviors suggest the formation of mass-enhanced Fermi liquid ground state analogous to that in $d$-electron heavy fermion compound LiV$_2$O$_4$.