Heat Dissipation in Molecular Junctions: Linking Molecules to Macroscopic Contacts

Abstract

Multiscale and hierarchical methods are becoming a paradigm for the understanding of complex physical phenomena. The concept can be applied to modern nanoelectronic devices where charge and thermal transport phenomena span a broad range of scales from nanometers up to millimeters, sometimes tightly interconnected as in the case of heat dissipation. This demand for the development of new stimulation tools that can cope with microscopic and macroscopic scales coupling different physical models. In this work progresses towards the realization of such integration schemes are presented. At the microscopic scale, the system is described using empirical or density-functional tight-binding descriptions (DFTB). Transport calculations are obtained using nonequilibrium Green’s functions methods that allow for calculations of coherent and incoherent transport and heat dissipation. At larger scales, effective medium equations are represented on finite-element meshes (FEM) to describe electronic and heat-transport phenomena with drift-diffusion or Fourier equations. Atomistic/FEM models are coupled imposing energy/current flux continuity at the boundaries. In this chapter an application of this scheme for the calculation of heat dissipation in molecular junctions is presented.