Coherently driven, ultrafast electron-phonon dynamics in transport junctions

Abstract

Although the vast majority of studies of transport via molecular-scale heterojunctions have been conducted in the (static) energy domain, experiments are currently beginning to apply time domain approaches to the nanoscale transport problem, combining spatial with temporal resolution. It is thus an opportune time for theory to develop models to explore both new phenomena in, and new potential applications of, time-domain, coherently driven molecular electronics. In this work, we study the interaction of a molecular phonon with an electronic wavepacket transmitted via a conductance junction within a time-domain model that treats the electron and phonon on equal footing and spans the weak to strong electron-phonon coupling strengths. We explore interference between two coherent energy pathways in the electronic subspace, thus complementing previous studies of coherent phenomena in conduction junctions, where the stationary framework was used to study interference between spatial pathways. Our model provides new insights into phase decoherence and population relaxation within the electronic subspace, which have been conventionally treated by density matrix approaches that often rely on phenomenological parameters. Although the specific case of a transport junction is explored, our results are general, applying also to other instances of coupled electron-phonon systems.

Is the Antiresonance in Meta-Contacted Benzene Due to the Destructive Superposition of Waves Traveling Two Different Routes around the Benzene Ring?

“…On the contrary, the quantum counterpart shown in Figure c,d is the case when a molecule is bound to metallic contacts. Among the many molecules showing DQI, − meta -connected benzene is a well-known chemical building block for this effect, − ,− although there are some arguments that DQI may not be visible or may be elusive for this configuration because of the shift of eigenenergies or because the dominant contribution comes from σ components. ,,,,,, The DQI is observed as a dip in the transmission spectra (Figure d). In the quantum case, the interference pattern is projected as a “transmission spectrum” in energy space, whereas in the classical case it is projected as “maximum absolute amplitude” in real space on the screen.…”