Abstract
We present scanning tunneling microscopy measurements of the (001) surface of a borocarbide single crystal at 4.2 K. In zero field, the conductance versus voltage characteristics recorded at various locations on the sample reproducibly provide a gap value of 2.2 meV. In a magnetic field of 1.5 and 0.375 T, the recordings of the conductance as a function of position reveal a regular square vortex lattice tilted by with respect to the crystalline axis. This unusual result is correlated with an in-plane anisotropy of the upper critical field at 4.2 K and is analyzed within the framework of Ginzburg-Landau theory.
- Received 16 January 1997
DOI:https://doi.org/10.1103/PhysRevLett.78.4273
©1997 American Physical Society