▎ 摘　　要

First-principles mechanistic investigations of field induced switching in an oligo(phenylene ethynylene) derivative attached to graphene nanoribbon leads are presented. It was shown that torsion of the oligomer unit causes an interruption of the conjugated pi-system along the nanoribbon direction, thereby drastically reducing the conductivity of the graphene wire. In this article, we investigate the dynamical aspects associated with the switching process, with particular emphasis on vibrational energy redistribution. First, a microscopic model Hamiltonian for the reaction path coupled to the phonons of the nanoribbon leads is parametrized using density functional theory calculations. The conformational change to access the energetically unfavored structure is induced by applying an external static electric field in the spirit of a traditional field effect transistor. Using the reduced density matrix formalism, we perform ground state quantum dynamics to simulate the complete switching cycle. The switching process is characterized by three distinct time scales originating from different physical phenomena and is found to be quantitative and reversible for experimentally accessible gate voltages. Analysis of the energy flow during the dynamics shows that energy is mainly dissipated to only a few transversal acoustic phonons of the graphene nanoribbon frame.