A simple model Hamiltonian is used to calculate the limit of zero-voltage resistance in a one-dimensional chain of one-state sites. The end atoms in the chain are considered to be chemisorbed to the surface of the metal electrodes and their interaction with the continuum of metal states (jellium model) is treated as in the Anderson–Newns chemisorption theory [1,2].

For this model, an exact solution can be obtained for the zero-voltage resistance within the formalism developed by Doyen and co-workers [3] for the calculation of the current in Scanning Tunneling Microscopy (STM). Applications of the results described in this article to the problem of molecular imaging in STM are presented elsewhere [4,5]. © 1993 John Wiley & Sons, Inc.