Thermoelectric Transport at the Nanoscale: A Density Functional Theory Perspective

Florian Eich
Max Planck Institute for the Structure and Dynamics of Matters, Hamburg, Allemagne
Vendredi 28 Avril 2017, 11h00
bibliothèque LCT, tour 12 - 13, 4^ème étage

In recent years there has been renewed interest in thermoelectric phenomena due to their potential impact for the development of sustainable energy sources. Shrinking thermoelectric devices to the atomic scale brings along the hope to improve the efficiency of converting temperature differences or heat flow into usable electric energy. Novel experimental techniques enable us to measure temperatures at the nanoscale, where quantum mechanical effects, such as interferences, are bound to play an important role. Applying thermodynamic concepts, such as temperature or heat flow, at the microscopic level raises a host of fundamental question, e.g.: Can we define a local temperature at atomic length scales? In my talk I will try to address these questions and provide an overview over a novel non-equilibrium density functional approach, dubbed time-dependent thermal density functional theory, which aims at an efficient description of thermoelectric transport phenomena at the nanoscale. I will explain Luttinger's idea of a mechanical proxy, or analogue, for local temperature variations in order to motivate our proposition to include the energy density as fundamental variable. Including the energy density into the density functional framework is not only required for a direct description the combined charge and energy flow through molecular electronic devices, but also completes the formal analogy of time-dependent density functional theory to classical hydrodynamics. Furthermore, I will present first applications of our approach to study steady-state and transient currents through simple models for nanoscale junctions.
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References :
[1] F. G. Eich, M. Di Ventra, and G. Vignale, Phys. Rev. Lett. 2014, 112, 196401.
[2] F. G. Eich, M. Di Ventra, and G. Vignale, Phys. Rev. B 2014, 90, 115116.
[3] F. G. Eich, M. Di Ventra, and G. Vignale, Phys. Rev. B 2016, 93, 134309.
[3] F. G. Eich, M. Di Ventra, and G. Vignale, J. Phys.: Condens. Matter 2017, 29, 063001.