We report angle resolved photoemission (ARPES) studies on electron-doped cuprate superconductor Sm2 - x Cex CuO4 (x = 0.14 and 0.18). A wide energy range scan shows clear "waterfall" effect at an energy scale close to 500 meV which is consistent with the value found in Nd2 - x Cex CuO4 (NCCO) but larger than that from hole-doped superconductors. High resolution results from both dopings show pseudo-gap effects that were observed in NCCO. However, the effects are found to be stronger than that observed in optimally doped NCCO. The overall electronic structure is well understood within a simple model in which a sqrt(2) × sqrt(2) static order is assumed. Both ARPES and optical measurements give the coupling strengths to the Q=(π / 2, π / 2) (due to the sqrt(2) × sqrt(2) order) to be about 0.1 eV, compatible with each other. The effect is strong enough to push the band near the nodal region below the Fermi energy, resulting in possible nodeless d-wave superconductivity where zero energy quasi-particle excitation is inhibited.
Bibliographical noteFunding Information:
This work is supported by the KICOS in K20602000008 and by KOSEF (R01-2006-000-10904-0). ALS and SSRL are operated by the DOE Office of Basic Energy Sciences.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics