Thermopower and resistivity for Nd1.85Ce0.15CuO4−δ single crystals: Existence of a holelike band

The in-plane resistivities (ρ) and thermopower (S) are studied in the Nd1.85Ce0.15CuO4+δ single crystals under different annealing conditions. In the optimally annealed samples, a positive thermopower indicates the existence of a holelike band. The resistivity and thermopower behaviors can be well described in a two-band model characterized by the different relaxation time (i.e. τh ∝ T−1 in holelike band and τe ∝ T−2 in electronic band). Moreover, the band shape is nearly unchanged and the Fermi level (EF) rises after the samples further deoxygenated. In contrast, the width of holelike band has been broadened and the Fermi level is nearly unchanged after the further oxygenation process.