Point-Contact Spectroscopy of Iron-Based Layered Superconductor LaO${}_{0.9}$F${}_{0.1-\hat{I}´}$FeAs

Abstract

We present point-contact spectroscopy data for junctions between a normal metal and the newly discovered F-doped superconductor LaO${}_{0.9}$F${}_{0.1-\hat{I}´}$FeAs (F-LaOFeAs). A zero-bias conductance peak was observed and its shape and magnitude suggests the presence of Andreev bound states at the surface of F-LaOFeAs, which provides a possible evidence of an unconventional pairing symmetry with a nodal gap function. The maximum gap value $\hat{I}{”}_0\approx 3.9\pm 0.7$meV was determined from the measured spectra, in good agreement with the recent experiments on specific heat and lower critical field.

5 pages, 4 figures