Effects of the intra-site Coulomb interaction on electron transport in an atom bridge

The effects of the intra-site Coulomb interaction on the electron transport in an atom-sized bridge (an atom bridge) between a metal surface and a tip of a scanning tunneling microscope are investigated with the aid of the Hubbard Hamiltonian. The second-order self-energy with respect to the Coulomb interaction in a single site approximation is taken into account in calculating for the conductance of the bridge. We examine the conductance variation as a function of the stretching length of the bridge in the case where an electron-hole symmetry is broken and two types of the conductance jumps roughly in units of 2e2/h and 4e2/h exist. Numerical results show that a valley structure and a quasi-plateau appear at the upper side of the conductance jumps roughly in units of 4e2/h at low temperatures and at high temperatures, respectively. On the other hand, the reduction of the conductance is small and monotonic at the conductance jumps roughly in units of 2e2/h. # 2001 Elsevier Science B.V. All rights reserved.