Large energy pseudogap in Nd2-xCexCuO4

We have investigated the temperature variation of optical spectra for single crystals of Nd2-xCexCuO4 (0.05 less than or equal to x less than or equal to 0.15). While little temperature variation has been observed in the optical spectrum of the x = 0.15 crystal, we have found a notable pseudogap as large as 0.2-0.4 eV at low temperature for the underdoped crystals (x < 0.15). Drude-like response also evolves concomitantly with the pseudogap formation. The onset temperature (T*) of the pseudogap decreases with electron doping. The origin of the pseudogap has been ascribed to the antiferromagnetic correlation. (C) 2004 Elsevier B.V. All rights reserved.