WAVEPACKETS AND INELASTIC TUNNELING

Using real-time numerical propagation techniques, we consider the tunnelling of electron wavepackets through potential barriers that possess internal dynamics. The models considered allow the study of the influence of localized surface vibrational modes on the tunnel current observed in scanning tunnelling microscopy. Non-resonant and resonant processes are considered. In the former case, we focus on the behaviour of the total tunnel current when the energy sweeps through an inelastic threshold. In the resonant case, we make contact with analytic theory and consider in detail, using a two-channel Breit-Wigner model, the physics underlying the resonant process, the physical origin of sum-rules obeyed by the tunnelling characteristic, and the conditions under which simple analytic theoretical results can be applied in general.