Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 22: Transport: Poster Session

TT 22.36: Poster

Wednesday, February 27, 2008, 14:00–18:00, Poster B

Bias-dependent electronic transport in nanowires — •Neng-Ping Wang and Stefan Heinze — Institute of Applied Physics, University of Hamburg, Jungiusstrass 11, 20355 Hamburg, Germany

Transport of electrons in nanoscale structures is of interest from a fundamental as well as an application point of view. Often nanoscale systems display nonlinear current-voltage characteristics, which make them interesting for device applications. Here, we report first principles calculations of bias-dependent ballistic transport in nanowires using the non-equilibrium Greens function method. The system under consideration is divided into a central scattering region attached to semi-infinite left and right leads. First, we use density functional theory (DFT) to calculate the electronic structure of the system. The DFT eigenstates are then transformed into a set of maximally localized Wannier functions (WFs). Using the WFs as localized orbitals, we construct the Hamiltonian of scattering region and leads, which is used for transport calculation. The coupling of the scattering region to the semi-infinite leads is described by the self-energies of the leads which we obtain with the particularly efficient decimation technique. We solve for the Green function of the system and calculate the transmission and current at low bias voltages.

As a first application of our approach, we study the I-V characteristics of Cu wires with a stretched bond as a function of the bond length. In order to explain the transport characteristics, we analyze the potential drop and non-equilibrium charge distribution as a function of the applied bias voltage.