Low-energy excitations around (π/2, π/2) points in the pseudogap phase of Nd₁.85Ce₀.15CuO₄

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.