Jungiusstr. 11, Hörsaal AP
SFB 668 - Kolloquium
Dr. C. Hess (Institut für Festkörperforschung, IFW Dresden):
Unconventional superconductivity in LiFeAs as seen by scanning tunneling microscopy and spectroscopy
In this talk, I will present recent results on the unconventional superconductor LiFeAs obtained by scanning tunneling micrsopcopy/spectroscopy (STM/STS). STM. STM/STS is an important probe for studying such superconductors. On the one hand it provides the possibility to directly measure the spatial variation of the order parameter in the presence of a magnetic vortex lattice, and thus the coherence length. On the other hand, the quasiparticle interference (QPI) which arises from quasiparticle scattering off impurities, and which sensitively depends on the superconducting wave function can be probed directly. LiFeAs belongs to the class of iron arsenide superconductors which have been discovered in 2008. This material possesses very clean and charge neutral cleaved surfaces without a surface state and is thus perfectly suited for STM/STS. Our QPI data are perfectly consistent with band structure data derived from angular reolved photoemission spectroscopy . However, the further analysis yields incompatibility with elementary s- or d-wave order parameters, suggestive of a more complex scenario . I will discuss these findings in the context of further experimental data and theoretical results.