CECAM - Theoretical Modeling of Transport in NanostructuresTheoretical Modeling of Transport in Nanostructures

Start: 2 June 14.30 End: 5 June 12.30 Interest in electronic transport properties of molecular wires and junctions has continuously increased during the last decades. The basis for this interest comes both from a fundamental scientific viewpoint and the possibility of technological applications as current electronic devices continue to shrink. Recently, for example, European researchers have measured the conductance of (i) a single hydrogen molecule [1], (ii) gold wires up to seven gold atoms long [2], and (iii) more complex hydrocarbon molecules [3,4]. The modelling of transport properties in (i) the phase coherent regime and (ii) Coulomb blockade regime has made similar strides where several European groups have independently developed atomistic computational methods to deal with the theoretically difficult non-equilibrium and finite-dimensional transport problem [5,6,7,8,9,10]. Especially methods using density functional theory to model phase coherent transport have been extended to include inelastic effects, spin polarized currents, and non-collinear magnetization. Despite the fact that many of the developments in modelling were archived by research groups in Europe, the lack of workshops/conferences hinder the dissemination and discussion of resent results. The main purpose of the suggested workshop is thus to increase the interactions between the researchers working on computational modelling of transport properties. In addition, many new developments including the modelling of spin polarized transport, inelastic scattering (phonon, magnon, photon), and thermoelectric properties (interaction of heat and electrical transport) are of interest. Current ab-initio methods based on density functional theory (DFT) allow the calculation of the transport properties of systems with hundreds of atoms [5,6,7,8,9,10], both at zero bias and under the presence of a finite voltage. These systems include molecules between metallic or semiconducting leads, atomic constrictions and chains, nanowires and nanotubes. In general, the transport properties of molecules strongly bound to the electrodes agree qualitatively but not quantitatively with experiments, with both the low-bias gap and absolute value of the current being too large [11]. However, the agreement is getting better as the codes and theory improve and excluding a few cases (like the archetypical Au-BDT junction [12]) the differences between theory and experiment are within one order of magnitude [13]. Several attempts have been made to increase the applicability of DFT methods, to include inelastic effects, spin degrees of freedom, non-collinear magnetism, the spin-orbit interaction, and beyond-DFT approaches like self-interaction effects, GW approaches, and time-dependent DFT (TDDFT). The aim at present is to develop feasible approaches to determine more accurately the transport properties of a wide range of molecules.

Theoretical Modeling of Transport in Nanostructures

Location: CECAM-HQ-EPFL, Lausanne, Switzerland

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