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

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/γ^2, is 16 times smaller than the universal value R_{KW}(=1.0 x 10^-5 μΩcm 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 ρ_0 near 25 kbar, where ρ_0 jumps by a factor of 7.

4pages, 3figures