Seminario Instituto Nicolás Cabrera
Jueves, 19 de Mayo de 2022, 16h30
Sala de seminarios, módulo 03, planta 5

Impact of atomic defects in the electronic states of  FeSe$_{1-x}$S$_{x}$
superconducting crystals

Yanina Fasano
Low Temperature Lab and Instituto Balseiro, Centro Atómico Bariloche,
Argentina
Leibniz Institute for Solid State and Materials Research, Dresden, Germany

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 tunnelling microscopy (STM) 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 as well as S-doped samples, irrespective  that in the latter case the
material presents extra crystal defects associated with the substitution of
Se by 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.