Spin-up and spin-down electron transport through a single-atom imperfect metallic wire: An analytical picture

Within a new perspective which includes the consideration of spin-up and spin-down electrons, a quantum-box approach is used to find a closed mathematical expression for the quantized electrical conductance of an imperfect point–metal contact. From this expression, both proper and improper fractions of the fundamental conductance quantum are obtained and discussed in the light of both resonant and off-resonant conduction states. Issues concerning Fermi energy and electrochemical potential are discussed. In addition, essential aspects related to the atom–lead coupling are examined; in particular, a tensor–dyadic formalism is introduced. Our results are found to be in excellent agreement with previous theoretical results and with experimental observations.