Interaction effects in low-dimensional conductors and superconductors

This dissertation considers interaction effects in zero- and quasi-one-dimensional metallic systems, both normal and superconducting. The effects studied in zero-dimensional systems include the influence of the Coulomb blockade on the quasiparticle spectrum and enhancement of the Josephson coupling in the superconducting double-island device; the Coulomb blockade in the system of a superconducting grain coupled to a normal lead. For the latter system a novel shape of the Coulomb staircase is predicted. In the case of quasi-one-dimensional systems, the work presents nonperturbative results for the thermodynamic and transport properties of disordered wires: For normal wires, the nonperturbative corrections to the specific heat are computed, and a new temperature scale, governing the behavior of these nonperturbative corrections, is found; in the case of superconducting wires it is shown that nonperturbative Coulomb effects lead to an additional channel of supercurrent decay, and thus contribute to the wire's resistance. Low-temperature transport in the superconductor/normal metal/superconductor junctions in the case where the superconducting order parameter has d-wave symmetry is also studied.