Title: In-gap bound states induced by a single nonmagnetic impurity in sign-preserving s-wave superconductors with incipient bands,
Abstract: We have investigated the in-gap bound states (IGBS) induced by a single
nonmagnetic impurity in multiband superconductors with incipient bands.
Contrary to the naive expectation, we found that even if the superconducting
(SC) order parameter is sign-preserving s-wave on the Fermi surfaces, the
incipient bands may still affect the appearance and locations of the IGBS,
although the gap between the incipient bands and the Fermi level is much larger
than the SC gap. Therefore in scanning tunneling microscopy experiments, the
IGBS induced by a single nonmagnetic impurity are not the definitive evidences
for the sign-changing order parameter on the Fermi surfaces. Our findings have
special implications for the experimental determination of the pairing symmetry
in the FeSe-based superconductors.