Abstract
Using angle-resolved photoemission spectroscopy (ARPES), we revealed the surface electronic structure and superconducting gap of , an intercalated FeSe-derived superconductor without antiferromagnetic phase or Fe-vacancy order in the FeSe layers, and with a superconducting transition temperature K. We found that layers dope electrons into FeSe layers. The electronic structure of surface FeSe layers in resembles that of except that it only contains half of the carriers due to the polar surface, suggesting similar quasiparticle dynamics between bulk and . Superconducting gap is clearly observed below , with an isotropic distribution around the electron Fermi surface. Compared with , the higher in might be attributed to higher homogeneity of FeSe layers or to some unknown roles played by the layers.
- Received 9 June 2015
DOI:https://doi.org/10.1103/PhysRevB.92.060504
©2015 American Physical Society