Scanning tunneling spectroscopy of superconducting LiFeAs single crystals: Evidence for two nodeless energy gaps and coupling to a bosonic mode

摘要

The superconducting compound, LiFeAs, is studied by scanning tunnelingmicroscopy and spectroscopy. A gap map of the unreconstructed surface indicatesa high degree of homogeneity in this system. Spectra at 2 K show two nodelesssuperconducting gaps with $\Delta_1=5.3\pm0.1$ meV and $\Delta_2=2.5\pm0.2$meV. The gaps close as the temperature is increased to the bulk $T_c$indicating that the surface accurately represents the bulk. A dip-humpstructure is observed below $T_c$ with an energy scale consistent with amagnetic resonance recently reported by inelastic neutron scattering.