The Righi-Leduc effect: on evidence of two-band electronic structure in

Several transport effects have been studied for a superconducting Nd 1.86 Ce 0.14 CuO 4 − δ single crystal. We present the normal-state temperature dependencies of the resisitivity (ρ), Hall coefficient (RH), thermal conductivity (κ) and Righi-Leduc coefficient (SRL). The main observation is that while SRL remains positive in the whole temperature range, the Hall coefficient changes its sign twice, at T≈50 and 250 K. Disagreement between signs of SRL and RH strongly suggests that both n-type (electron-like) and p-type (hole-like) charge carriers are present in the material. We have concluded that the heat transport is dominated by p-carriers, whereas p- and n-contributions for charge transport seem to be comparable. Furthermore we have found that the Lorentz number of the hole-like subsystem obeys the Wiedemann-Franz law.