Bogoliubov Electronic Structure at Individual Impurity Atoms in LiFeAs

Individual impurity atoms in a superconductor can strongly perturb the surrounding electronic environment and can therefore be used to probe high-temperature superconductivity at the atomic scale. Spectroscopic imaging scanning tunneling microscopy (SI-STM) is an ideal technique for the study of such effects. This has provided the motivation for several theoretical studies predicting the spatial and energetic structure of Bogoliubov electronic states at single impurity atoms in Fe-based superconductors. Here we report on a type of impurity atom that forms a strong in-gap quasi-particles interference (QPI) pattern nearby in the Fe-based superconductor LiFeAs. Our result puts a number of restrictions on theoretical studies of Fe-based superconducting mechanism.