Field-Induced Funneling of Vibrational Energy into High-Frequency Modes in Molecular Junctions Far from Equilibrium

The ability to control the energy content of specific molecular vibrations is essential for realizing mode-selective chemistry. Single-molecule junctions far from equilibrium were proposed as potential platforms for this purpose by utilizing different bias polarities for funneling energy into different molecular modes. Here, we show that vibrational energy can be funneled into (or out of) a specific molecular mode even under a fixed static bias, via external periodic driving (or changing the temperature) of the fermion reservoirs in the molecular junction. Indeed, changes in the charge-carrier distributions within the driven reservoirs induce changes in the balance between vibrational cooling and heating pathways (induced by charge transport), in a way which depends sensitively on the different mode frequencies and vibronic couplings. Conditions under which this proposed mechanism should induce pronounced mode-selective excitation are demonstrated and discussed.