Abstract
Polarized electronic Raman scattering from the NCCO superconductor at optimal
electron doping (T_c=22 K) reveals the formation of an anisotropic pseudogap
below a characteristic temperature T* ~ 220 K and energy E*_g = 850 cm-1. Below
T* a pronounced suppression of the incoherent spectral weight below E*_g in the
nodal directions of k-space is observed. This is concomitant with the emergence
of long-lived excitations in the vicinity of the (\pi/2, \pi/2) points that do
not contribute to the optical conductivity.