A Model For Point Contacts Between A Normal Metal And A Superconductor In An Applied Magnetic Field

The BTK model for charge transport in a normal metal/superconductor point contact, with elastic and inelastic quasiparticle scattering, is modified to include the effect of an applied magnetic field. A two channel model of the form G$_{S}$(h, T) = h$^{a}$G$_{NN}$ + (1 - h$^{a})$ G$_{NS}$(T) is assumed, where h is the reduced magnetic field, G$_{S}$(h, T) is the contact conductance, G$_{NN}$ is the normal channel contribution and G$_{NS}$(T) is the superconducting channel contribution. The value of the field exponent, a, is obtained by first extracting the BTK parameters for the contact at zero applied field. Using these parameters, a is fit to the transport data as a function of applied field, at fixed temperature. Several case studies over a wide range of BTK parameters will be discussed. Best fits to the data indicate that within the assumptions of this model, a = 2.