Doping Dependence of Pseudogap and Related Charge Dynamics inNd2−xCexCuO4

A notable pseudogap ( ${\Delta }_{\mathrm{PG}}$ as large as 0.2–0.4 eV) has been found below a characteristic temperature $T^{*}$ in the optical conductivity spectrum for metallic but nonsuperconducting crystals of ${\mathrm{Nd}}_{2-x}{\mathrm{Ce}}_x{\mathrm{CuO}}_4$ $(x<\mathrm{}0.15\mathrm{})$. The ${\Delta }_{\mathrm{PG}}$ and $T^{*}$ decrease with doping $x$, holding the relation of ${\Delta }_{\mathrm{PG}}\approx {10k}_{\mathrm{B}}{T}^{*}$. The Drude-like component is observed to evolve concomitantly with the pseudogap. The $T^{*}$ almost coincides with another characteristic temperature $T_0$ that scales the Hall coefficient. These results indicate that the charge transport in the underdoped region is under the strong influence of the pseudogap state.