Impact of atomic defects in the electronic states of FeSe 1−x S x superconducting crystals

• Published in: JPhys materials Vol. 5; no. 4; pp. 44008 - 44018
• Main Authors: Aragón Sánchez, Jazmín, Amigó, María Lourdes, Belussi, Cristian Horacio, Ale Crivillero, María Victoria, Suárez, Sergio, Guimpel, Julio, Nieva, Gladys, Esteban Gayone, Julio, Fasano, Yanina
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.10.2022
• Subjects: atomic scale defects; electronic core levels; Fe-based superconductors; STM; XPS
• ISSN: 2515-7639; 2515-7639
• DOI: 10.1088/2515-7639/ac9dc1

Abstract The electronic properties of Fe-based superconductors are drastically affected by deformations on their crystal structure introduced by doping and pressure. Here we study single crystals of FeSe 1 − x S x and reveal that local crystal deformations such as atomic-scale defects impact the spectral shape of the electronic core level states of the material. By means of scanning tunneling microscopy we image S-doping induced defects as well as diluted dumbbell defects associated with Fe vacancies. We have access to the electronic structure of the samples by means of x-ray photoemission spectroscopy (XPS) and show that the spectral shape of the Se core levels can only be adequately described by considering a principal plus a minor component of the electronic states. We find this result for both pure and S-doped samples, irrespective that in the latter case the material presents extra crystal defects associated to doping with S atoms. We argue that the second component in our XPS spectra is associated with the ubiquitous dumbbell defects in FeSe that are known to entail a significant modification of the electronic clouds of surrounding atoms.