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

TL;DR

This study uses point-contact spectroscopy to investigate the superconducting properties of LaO$_{0.9}$F$_{0.1-\delta}$FeAs, revealing evidence of unconventional pairing and measuring the superconducting gap.

Contribution

First point-contact spectroscopy analysis of LaO$_{0.9}$F$_{0.1-\delta}$FeAs showing signs of unconventional pairing symmetry and surface Andreev bound states.

Findings

Zero-bias conductance peak indicating Andreev bound states

Superconducting gap $\Delta_0 oughly 3.9$ meV

Consistent with other thermodynamic measurements

Abstract

We present point-contact spectroscopy data for junctions between a normal metal and the newly discovered F-doped superconductor LaO$_{0.9}$F$_{0.1-\delta}$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 $\Delta_0\approx3.9\pm0.7$meV was determined from the measured spectra, in good agreement with the recent experiments on specific heat and lower critical field.