Graphite-superconductor junctions as a probe of order-parameter symmetry

We discuss a method for determining the order-parameter symmetry of quasi-one- and quasi-two-dimensional unconventional superconductors by the use of graphite-superconductor junctions. The use of a graphite gate voltage, in combination with a bias tunneling voltage, allows access to more information concerning gap values on the Fermi surface than with conventional tunneling spectroscopy, where only a bias voltage is employed. In particular, the use of a gate voltage allows one to tune the momentum-space size of the tunneling region, thus accessing gap values over local regions of the superconductor Fermi surface, in contrast to conventional tunneling techniques.