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We have performed scanning tunneling microscopy measurements on the stoichiometric iron pnictide superconductor LiFeAs. After cleaving single crystalline samples, we observe a flat surface which can be investigated by scanning tunneling spectroscopy.
At temperatures T=15K we see that the superconducting gap vanishes. Independent on the temperature we observe an asymmetry in the spectra with additional features near the Fermi energy and 50mV above EF. The good agreement of our results with model calculations for the tunneling conductance allows us to draw conclusions about the low energy properties of the superconducting system. Furthermore, the STM data of the sample surface reveal a small amount of impurity sites, which can be assigned to particular structural defects. |
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