Electronic devices composed of single molecules constitute the ultimate limitin the continued downscaling of electronic components. A key challenge forsingle-molecule electronics is to control the temperature of these junctions.Controlling heating and cooling effects in individual vibrational modes, can inprinciple, be utilized to increase stability of single-molecule junctions underbias, to pump energy into particular vibrational modes to performcurrent-induced reactions or to increase the resolution in inelastic electrontunneling spectroscopy by controlling the life-times of phonons in a moleculeby suppressing absorption and external dissipation processes. Under bias thecurrent and the molecule exchange energy, which typically results in heating ofthe molecule. However, the opposite process is also possible, where energy isextracted from the molecule by the tunneling current. Designing a molecular'heat sink' where a particular vibrational mode funnels heat out of themolecule and into the leads would be very desirable. It is even possible toimagine how the vibrational energy of the other vibrational modes could befunneled into the 'cooling mode', given the right molecular design. Previousefforts to understand heating and cooling mechanisms in single moleculejunctions, have primarily been concerned with small models, where it is unclearwhich molecular systems they correspond to. In this paper, our focus is onsuppressing heating and obtaining current-induced cooling in certainvibrational modes. Strategies for cooling vibrational modes in single-moleculejunctions are presented, together with atomistic calculations based on thosestrategies. Cooling and reduced heating are observed for two different coolingschemes in calculations of atomistic single-molecule junctions.
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