Obtaining tetragonal FeAs layer and superconducting KxFe2As2 by molecular beam epitaxy

Atomic characterization on tetragonal FeAs layer and engineering FeAs superlattices is highly desirable to get deep insight into the multi-band superconductivity in iron-pnictides. We fabricate the tetragonal FeAs layer by topotactic reaction of FeTe films with arsenic and then obtain KxFe2As2 upon potassium intercalation using molecular beam epitaxy. The in-situ low-temperature scanning tunneling microscopy/spectroscopy investigations demonstrate characteristic root 2 x root 2 reconstruction of the FeAs layer and stripe pattern of KxFe2As2, accompanied by the development of a superconducting-like gap. The ex-situ transport measurement with FeTe capping layers shows a superconducting transition with an onset temperature of 10 K. This work provides a promising way to characterize the FeAs layer directly and explore rich emergent physics with epitaxial superlattice design.

Automated summary

This study provides deep insights into the multi-band superconductivity in iron-pnictides by characterizing the tetragonal FeAs layer and engineering FeAs superlattices. The results demonstrate the characteristic reconstruction and superconducting gap formation in the FeAs layer and stripe pattern of KxFe2As2 after potassium intercalation. The ex-situ transport measurement shows a superconducting transition with an onset temperature of 10 K in the samples with FeTe capping layers.