Observation of mode-like features in tunneling spectra of iron-based superconductors

We report scanning tunneling microscopy/spectroscopy (STM/STS) studies on iron-based superconductors of Ba_1-xK_xFe₂As₂ and nearly optimally doped Fe(Te,Se). Mode-like features were observed universally outside the superconducting gaps in the tunneling spectra, which are similar to our previous observations in other samples and can be ascribed to the interaction between electrons and spin excitations. Furthermore, an almost linear relationship between the superconducting gaps and the superconducting transition temperatures was noted and should also be taken into account in understanding the mechanism of iron-based superconductors.