Optical Properties of (pr,ce) 2 Cuo 4

We studied the optical conductivity of electron doped Pr1−xCexCuO4 from the underdoped to the overdoped regime. The observation of low to high frequency spectral weight transfer reveals the presence of a gap, except in the overdoped regime. A Drude peak at all temperatures shows the partial nature of this gap. The close proximity of the doping at which the gap vanishes to the antiferro-magnetic phase boundary leads us to assign this partial gap to a spin density wave. 1. Introduction The electron and hole doped cuprates phase diagram shows a global symmetry. However, many aspects of the electron doped compounds, including the nature of the superconducting gap, the behavior of the normal state charge carriers, and the presence of a normal state (pseudo)gap are still unclear. A pseudogap phase is now well established on the hole doped side [1]. In Bi 2 Sr 2 CaCu 2 O 8+δ , angle resolved photoemission spectroscopy measurements (ARPES) indicate a pseudogap opening along the (0, π) direction in k space [2]. However, the in-plane optical conductivity does not show any direct evidence of this pseudogap [3]. The optical conductivity of non superconduct-ing Nd 2−x Ce x CuO 4 (NCCO) single crystals (x = 0 to 0.125) suggests the opening of a high energy partial gap well above T N eel [4]. Low temperature ARPES reveals a Fermi surface characterized by the presence of pockets [5]. We determined the temperature evolution of the optical conductivity in a set of Pr 2−x Ce x CuO 4 thin films. Our data reveals the onset of a " high energy " partial gap below a characteristic temperature T W which evolves with doping.