Electric Current Fluctuations Induced by Molecular Vibrations in the Adiabatic Limit: Molecular Dynamics-Driven Liouville von Neumann Approach

We investigate time-dependent electron transport through a molecular junction in the adiabatic limit at the density-functional tight-binding level using the molecular dynamics-driven Liouville von Neumann (MD-DLvN) approach. When electron transport involves nuclear dynamics at finite temperature (∼70 K) within the NVE ensemble, we find that the steady-state current cannot be achieved even for a very short molecule (trans-fumaronitrile). Furthermore, to establish a relationship between electric current fluctuations and molecular vibrations, we analyze the similarities and differences between the current noise spectra and the MD power spectra. Our simulations show that not all normal modes can bring about current fluctuations. Furthermore, when a normal mode satisfies a particular symmetry, the normal mode can lead to frequency doubling of current fluctuations. This investigation offers new directions for studying electronic dynamics in a nonequilibrium open quantum system.