Anomalous Pressure Dependence of Kadowaki-Woods ratio and Crystal Field Effects in Mixed-valence YbInCu4

TL;DR

This study investigates how pressure affects the Kadowaki-Woods ratio and electronic properties of YbInCu4, revealing significant deviations from universal behavior linked to changes in orbital degeneracy and carrier density.

Contribution

It provides the first detailed analysis of pressure-induced variations in the Kadowaki-Woods ratio and crystal field effects in a mixed-valence compound.

Findings

Kadowaki-Woods ratio sharply increases with pressure.

Residual resistivity jumps near 25 kbar.

Deviation from universal ratio explained by changes in degeneracy and carrier density.

Abstract

The mixed-valence (MV) compound YbInCu4 was investigated by electrical resistivity and ac specific heat at low temperatures and high pressures. At atmospheric pressure, its Kadowaki-Woods (KW) ratio, A/\gamma ^2, is 16 times smaller than the universal value R_{KW}(=1.0 x 10^-5 \mu \Omega cm mol^2 K^2 mJ^-2), but sharply increases to 16.5R_{KW} at 27 kbar. The pressure-induced change in the KW ratio and deviation from R_{KW} are analyzed in terms of the change in f-orbital degeneracy N and carrier density n. This analysis is further supported by a dramatic change in residual resistivity \rho_0 near 25 kbar, where \rho_0 jumps by a factor of 7.