ANISOTROPIC TUNNELING AND RESISTIVITY IN HIGH-TEMPERATURE SUPERCONDUCTORS

We discuss the tunneling characteristics expected within an anisotropic metal using the marginal-Fermi-liquid phenomenology. Although there is no modification of the density of states, we show it to be natural that tunneling matrix elements lead to an anisotropic conductance, which is typically V-shaped for c-axis tunneling, and almost flat for in-plane tunneling. We suggest that this behavior is directly related to the observation of resistive upturns in the c-axis conductivity of disordered samples.