Vibrationally coupled electron transport in single‐molecule junctions: The importance of electron–hole pair creation processes

Abstract

Vibrationally coupled electron transport through singlemolecule 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, electronhole 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.

Effect of broadening in the weak-coupling limit of vibrationally coupled electron transport through molecular junctions and the analogy to quantum dot circuit QED systems

“…4a-b). While the former are sufficient to understand the electronic population on a qualitative level, the vibrational excitation characteristics can only be understood if the effect of electron-hole pair creation processes is taken into account [9,23,82].…”

“…A bias voltage can be applied such that electrons tunnel through the molecule. Due to the small size and mass of a molecule, the tunneling electrons are likely to interact with the molecules vibrational modes, leading to inelastic tunneling processes where vibrational motion is excited and deexcited [8,14,20,23,[40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. This behavior has been observed in a number of experiments [57][58][59][60][61][62][63][64][65][66][67][68][69][70].…”

Decoherence and lead-induced interdot coupling in nonequilibrium electron transport through interacting quantum dots: A hierarchical quantum master equation approach

“…Decoherence phenomena arising from electronvibrational mode coupling in quantum dot systems 27,28 or single-molecule junctions 26,29 have been studied; one striking result is a pronounced temperature dependence of the current. 8,26,30 In quantum dot arrays, interference effects are suppressed by spin-flip processes. 15,31,32 A similar effect is observed in InSb nanowires, where interaction-or correlationinduced resonances occur.…”

Calculation of Electronic Lifetimes in Molecular Junctions

“…Then the electron hops to the right/left electrode and the molecule returns to the electronic ground state, but may be left in a vibrational excited state. The vibrational excited state can decay via the excitation of an electron-hole pair [19,20]. (1) The first three terms denote the Hamiltonian for electrons in the independent molecule, the left and right noninteracting metallic electrodes, respectively [21,24],…”