STM/STS study of the superconducting gap in SmFeAsO1−xFx

• We report the electron tunneling study in different Tc samples of SmFeAsO1−xFx (x=0, 0.045, 0.046, 0.069) by using low temperature UHV-STM/STS.
• The superconducting gap and the pseudogap are observed on superconducting samples (x=0.045, 0.046, 0.069).
• We also observed the gap structure on non-superconducting sample. The gap structure is similar to the superconducting gap on superconducting samples.
• The gap size is not scale to transition temperature.

We report an electron tunneling study of SmFeAsO1−xFx in the low doping region (x=0, 0.045, 0.046, 0.069) by low temperature UHV-STM/STS. Superconducting gaps are observed for each superconducting sample x=0.045 (Tc=12.9 K), x=0.046 (Tc=32.9 K) and x=0.069 (Tc=46.9 K). We obtained corresponding superconducting gap size of ΔSC=9.5±0.5meV, 9.75±0.25 meV and 11±1 meV. While Tc increases, ΔSCΔSC is kept the same. This suggests that the effective attractive interaction is the same and that there is some mechanism that suppresses the superconductivity in the low doping region. On the other hand, similar gap structures were found in a non-superconducting sample with x=0 at 7.8 K. The obtained gap size was ΔN=8.5±1.5meV, which is almost the same as the superconducting gap in the superconducting samples (x=0.045, 0.046, 0.069).