Tunneling in a spin-density-wave superconductor

The differential tunneling conductance of normal-insulator-superconductor (NIS) and superconductor-insulator-superconductor (SIS) junctions is calculated for polycrystalline superconducting films which have either a spiral or linear spin-density-wave (SDW). In the NIS case, the SDW induced-gap anisotropy causes an enhancement of the low-bias tunneling conductance by several orders of magnitude, compared to that predicted by (isotropic) Bardeen-Cooper-Schrieffer theory. In the SIS case, the tunneling conductance is also enhanced, though the effect is less spectacular. The calculations are compared with existing experimental data on Al-Pb junctions. Fairly good agreement is found, which supports the speculation that Pb might have a SDW ground state.