Low-temperature scanning tunneling spectroscopic observation of vortex in a NbCxN1−x thin film

Abstract
Scanning tunneling spectroscopic studies were performed on superconducting NbCxN1−x thin films at 4.2 K. An image of a spatial variation of a gap obtained in a magnetic field of 0.3 T showed a clear vortex lattice. Two types of the spatial variations of the local density of states around the vortex cores were observed. Type I had a normal center in the core, and a gap variation around the core was consistent with a theory for dirty limit superconductors. Type II did not have a normal center and the origin of this core is not yet clear.