Fermi Surface Effect on Lorenz Number of Correlated Metal

Abstract

We investigate an effect that an ideal Lorenz number $L_{\mathrm{i}}$ of correlated metal shows peculiar Fermi surface dependence, which is caused by the onset of a particular channel of Umklapp scattering. We evaluate $L_{\mathrm{i}}$ for some simple models and transition metals, and note that $L_{\mathrm{i}}$ for Na${}_x$CoO${}_2$ decreases sensitively as $x$ approaches an Umklapp threshold around $x_c\simeq 0.6$.

6pages, 4figures