Abstract
We present tunneling data from superconducting and its parent compound, . In the superconductor, clear coherencelike peaks are seen across the whole field of view, and their analysis reveals nanoscale variations in the superconducting gap value, . The average peak-to-peak separation gives a of , which exceeds the BCS weak coupling value for either - or -wave superconductivity. The characteristic length scales of the deviations from the average gap value and of anticorrelations observed between the gap magnitude and both the zero-bias conductance and coherence peak strength match well with the average separation between the Co dopant ions in the superconducting FeAs planes.
- Received 8 April 2009
DOI:https://doi.org/10.1103/PhysRevB.79.220517
©2009 American Physical Society