Transport Properties And Noise Of Low-Dimensional Conductors

The subject of this thesis is (1) the description of the conducting properties of layered high-temperature superconductors along the least conducting direction (perpendicular to the planes) and (2) the frequency dependence of the noise and conductance of one- and two-dimensional conductors. Both topics stress the potential importance of collective charge fluctuations in low-dimensional conductors. The thesis consists of two (almost) independent parts. In the first part, a theoretical model of conduction between the planes ( c-axis conduction) of layered high-temperature superconductors in the normal state is presented. The main idea of the model is that tunneling between planes is hindered by voltage fluctuations between the tunneling points. The question of the conservation of electron momentum parallel to the planes during tunneling is carefully examined. Various spectra of voltage fluctuations are evaluated in order to analyze the applicability of the model. The temperature and frequency dependencies of the c-axis conductivity are calculated from the premises of the proposed model. Experimental data are summarized and analyzed in the framework of this model. The relevance of the proposed model for other layered systems is discussed. In the second part, the frequency dependence of conductance and Johnson-Nyquist noise is calculated for one-dimensional wires and two-dimensional films. In low-dimensional conductors, collective effects become important even at low frequencies and lead to the predicted novel effects. Two different ways to derive the spectrum of charge fluctuations are demonstrated. Certain frequency dependencies of noise and conductance for one-dimensional wires and two-dimensional films, which can be subjected to experimental test, are predicted.U of I OnlyThesi