Transport in mesoscopic superconductors and superconducting/normal metal contacts

The charging energy is important for a mesoscopic body with small capacitance to the environment. Connecting the small island via low capacitance, high resistance tunnel junctions, the current through the resulting structure will depend upon the charge of the island - charge that can be applied via a gate electrode. For a normal metal island, the current varies periodically with the charge; the periodicity is the electron charge e. If the island is superconducting, the period, e or 2e, depends upon whether the superconducting energy gap is less than or larger than the charging energy. This parity effect can be used to study possible nodes in the gap function of a high-T-C, superconductor. The charge transport through a mesoscopic conductor can be controlled by a phase difference between superconducting contacts to the normal conductor. If the phase difference is applied via a superconducting loop connected to the contacts, the conductance varies periodically with the flux or the current through the loop and the period is the quantized flux unit. The oscillation amplitude is temperature dependent as expected from theoretical predictions.