NSTI Nanotech 2009

Controlled Electron Transport Through Single Molecules

V. Garcia-Suarez and C. Lambert
Lancaster University, UK

Keywords: simulation, Ab initio


Ab initio methods based on density functional theory (DFT) and the non-equilibrium Green functions formalism (NEGF) are becoming increasingly popular to obtain the transport properties of nanoscale systems. We present an efficient implementation of such methods in the Smeagol code. Smeagol uses the Hamiltonian provided by the DFT code SIESTA, which employs pseudopotentials and linear combination of atomic orbitals, and applies NEGF to calculate the density matrix, transmission coefficients and I-V characteristics. We show some examples of simulations of molecular electronic systems, which include small molecules, insulating and conducting molecules between magnetic and non-magnetic leads and molecules encapsulated in carbon nanotubes. These calculations allow us to predict several properties and effects that match those of the typical electronic components, such as negative differential resistance, magnetoresistance and sensing. We shall also discuss a range of geometrical methods for controlling electron transport through single molecules, including: • ring rotations in conjugated molecules; • Fano resonances associated with side groups attached to rigid backbones; • varying the distance between conducting electrodes; • rotating the magnetic moments of carbon-nanotube-encapsulated molecules.
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