A model for the Josephson junction is constructed based on two macroscopic angular momentum vectors. These vectors, which interact via a Heisenberg-like Hamiltonian, are defined using Anderson's pseudospin concept in superconductivity. Along with this, a new state vector, which affords a more complete description of the constant-charge-imbalance mode of the junction, is explicitly constructed. The resulting equations of motion lead directly to the basic Josephson results and at the same time provide a simple physical picture for the dynamical behavior of the junction. Both the Anderson (n,(phi)) and Feynman two-state models of the junction are shown to be equivalent to a restricted form of the angular momentum approach. The process of formulating the junction problem in terms of pseudo-angular-momentum together with the above identification constitutes a microscopic derivation of the Feynman method. A perturbation theory calculation is carried out within the full pseudo-angular-momentum equations of motion to determine how this approach differs from the earlier ones.

No description available.

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 100-102).

Not available / text

published_or_final_version / abstract / toc / Physics / Doctoral / Doctor of Philosophy

No description available.

<p>We report on graphene-based Superconductor-Normal metal-Superconductor Joseph- son junctions with contacts made from lead. The high transition temperature of this superconductor allows us to observe the supercurrent branch at temperatures up to &#1113094; 2 K. We are able to detect a small, but non-zero, resistance despite the Josephson junctions being in the superconducting state. We attribute this resistance to the phase diffusion regime, which has not been yet identified in graphene. By measuring the resistance as a function of temperature and gate voltage, we can further charac- terize the nature of electromagnetic environment and dissipation in our samples. In addition we modulate the critical current through grapehene by an external magnetic field; the resulting Fraunhofer interference pattern shows several periods of oscilla- tions. However, deviations from the perfect Fraunhofer pattern are observed, and their cause is explained by a simulation that takes into account the sample design.</p> / Dissertation

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Hong Kong, 2000. / Includes bibliographical references.

Ulm, Univ., Diss., 2000.