Signposts towards the pairing mechanism of pnictide superconductors unveiled by scanning tunneling microscopy

YANINA FASANO

Kosice

Conferencia; Charla invitada en la International Cryoconference 2010; 2010

Kosice University

We probe the local quasiparticles density-of-states in recently available micron-sized SmFeAsO1-xFx single-crystals by means of Scanning Tunnelling Spectroscopy. Systematic spectral featuresresemble those of cuprates, namely a particle-hole asymmetric background, a V-shaped low-biasconductance, and a dip-hump-like structure developed at energies larger than the gap. This lastfeature can be ascribed to the coupling of quasiparticles to a collective mode, quite likely a resonantspin mode as the one detected in other pnictides. From our data we infer that the energy of thecollective mode decreases when the pairing strength increases, as also reported in cuprates. Ourfindings suggest that the collective mode revealed in our study is intimately related tosuperconductivity, supporting spin-fluctuation-mediated pairing in pnictides.