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Abstract:
The order parameter and pairing mechanism for superconductivity in
heavy-fermion compounds are still poorly understood. Scanning tunneling
microscopy and spectroscopy at ultralow temperatures can yield important
information about the superconducting order parameter and the gap
structure. Here, we study the first heavy-fermion superconductor,
CeCu2Si2. Our data show the superconducting gap which is not fully
formed and exhibits features that point to a multigap order parameter.
Spatial mapping of the zero-bias conductance in magnetic field reveals
the vortex lattice, which allows us to unequivocally link the observed
conductance gap to superconductivity in CeCu2Si2. The vortex lattice is
found to be predominantly triangular with distortions at fields close to
similar to 0.7H(c2).
