Vibrationally coupled electron transport through single-molecule junctions is
considered. Reviewing our recent theoretical work, we show that electron-hole
pair creation processes represent the key to understand the vibrational
excitation characteristic of a single-molecule contact. Moreover, these
processes can lead to a number of interesting transport phenomena such as, for
example, negative differential resistance, rectification, mode-selective
vibrational excitation and a pronounced temperature dependence of the
electrical current. Thus, electron-hole pair creation processes are crucial to
elucidate the basic mechanisms of vibrationally coupled electron transport
through a single-molecule contact, despite the fact that these processes do not
directly contribute to the electrical current that is flowing through the
junction.Comment: 13 article pages, 13 figures; review article submitted to PSS (b) for
the special issue 'Quantum transport at the molecular scale
