Resonant tunneling in high-Tc superconductors

A review is presented of the author's work on resonance tunneling as an electron transport mechanism along the c-axis in high-temperature layered cuprates. Problem formulation is given, qualitative aspects of the mechanism are described, and physical properties calculated. Comparisons are made with experimental data for the temperature dependence of normal conductivity, the frequency dependence of optical conductivity, and stationary supercurrent along the c-axis. For the latter property, resonance tunneling coherence of different centres is shown to be of crucial importance. Weakened interplane coupling and vortex fluctuations are invoked to explain the sharp drop in T-c and the rise in the 2 Delta(0)/T-c ratio with decreasing oxygen content. Simple example models are given to demonstrate major aspects of resonance tunneling.