Common (π,π) Band Folding and Surface Reconstruction in FeAs-Based SuperconductorsSupported by the National Key Research and Development Program of China (Grant Nos. 2016YFA0300300, 2017YFA0302900, 2018YFA0704200 and 2019YFA0308000), the National Natural Science Foundation of China (Grant Nos. 11888101, 11922414 and 11874405), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB25000000), the Youth Innovation Promotion Association

Abstract

High resolution angle-resolved photoemission spectroscopy (ARPES) measurements are carried out on CaKFe4As4, KCa2Fe4As4F2 and (Ba0.6K0.4)Fe2As2 superconductors. Clear evidence of band folding between the Brillouin zone center and corners with a (π,π) wave vector has been found from the measured Fermi surface and band structures in all the three kinds of superconductors. A dominant surface reconstruction is observed on the cleaved surface of CaKFe4As4 by scanning tunneling microscopy (STM) measurements. We propose that the commonly observed reconstruction in the FeAs-based superconductors provides a general scenario to understand the origin of the (π,π) band folding. Our observations provide new insights in understanding the electronic structure and superconductivity mechanism in iron-based superconductors.