Current-induced heating and cooling in molecular junctions

DIPC Seminars

Giuseppe Foti (Institute of Physics, Czech Academy of Science, Prague)
Donostia International Physics Center
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Current-induced heating and cooling in molecular junctions The delicate balance between heat generation and dissipation in molecular junctions subject to an external bias is strongly influenced by the electronic structure of the metal-molecule-metal system. The presence of sharp molecular resonances close to the Fermi window can, in fact, favor the transfer of energy from molecular vibrations to the electrodes or, on the other hand, promote the efficient emission of localized vibrational quanta with important implications for the stability of the junction [1,2]. In this talk I will present our _first principles_ calculations based on density functional theory (DFT) in combination with the nonequilibrium Green's function formalism (NEGF) addressing the important role of the electronic structure in the heating and cooling dynamics (HCD) of molecular junctions under an applied bias. I will show how the atomistic details of electrode terminations as well as the presence of contaminants adsorbed nearby the junction can lead to qualitatively different HCD of N-heterocyclic carbenes (NHCs) under an applied bias [3, 4]. Also, I will present our recent efforts in understanding the origin of vibrational instabilities in molecular wires with broken conjugation. [1] J.-T. Lü, P. Hedegård, and M. Brandbyge, Phys. Rev. Lett. 107, 046801 (2011) [2] M. Engelund, J. A. Fürst, A. P. Jauho, and M. Brandbyge Phys. Rev. Lett. 104, 036807 (2010) [3] G. Foti and H. Vázquez, J. Phys. Chem. C 121, 1082 (2017) [4] G. Foti and H. Vázquez, Beilstein J. Nanotechnol. (accepted)