The normal state properties of the recently discovered ferropnictide superconductors might hold the key to understanding their exotic superconductivity. Using point-contact spectroscopy we show that Andreev reflection between an epitaxial thin film of Ba(Fe0.92Co0.08)2As2 and a silver tip can be seen in the normal state of the film up to temperature T∼1.3Tc, where Tc is the critical temperature of the superconductor. Andreev reflection far above Tc can be understood only when superconducting pairs arising from strong fluctuation of the phase of the complex superconducting order parameter exist in the normal state. Our results provide spectroscopic evidence of phase-incoherent superconducting pairs in the normal state of the ferropnictide superconductors.
ASJC Scopus subject areas
- Physics and Astronomy(all)