Angle resolved photoemission studies on Sm 2− xCe xCuO 4: remnant Fermi surfaces and coupling to (π,π) scattering

Abstract

We report high-resolution angle-resolved photoelectron spectroscopy studies on electron doped superconductors, Sm 2− x Ce x CuO 4 ( x=0 and 0.15). The results on the undoped ( x=0) samples show Cu–O anti-bonding states with an overall dispersion of about 0.3 eV which is similar to other insulating cases. The low energy dispersive feature quickly looses intensity before it reaches the Fermi energy near the anti-ferromagnetic zone boundary, showing a remnant behavior of the original Fermi surface (FS). In doped cases ( x=0.15), FS mapping shows suppressed intensities at the Fermi energy where the FS crosses the anti-ferromagnetic zone boundary. This is similar to what was observed on another electron doped superconductor Nd 1.85Ce 0.15CuO 4 which was ascribed being due to the formation of a high-energy pseudogap assisted by Q =( π,π) scattering. Similarities and differences in comparison to other compounds are discussed.