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DIPC–PAMS theory workshop

Towards reality in modelling of molecular electronics

June 13-17, 2016 ▪ Donostia-San Sebastián, Spain

Invited talk

Steady-state density functional theory for finite bias conductances

S. Kurth1,2, G. Stefanucci3,4

1Dept. of Materials Physics, Univ. of the Basque Country UPV/EHU, San Sebastian, Spain

2IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

3Dept. of Physics, Univ. of Rome "Tor Vergata", Rome, Italy

4INFN, Frascati, Italy

In the framework of density functional theory a formalism to describe electronic transport in the steady state is proposed which uses the density on the junction and the steady current as basic variables. In a finite window around zero bias, a one-to-one map is established between the basic variables and both local potential on as well as bias across the junction. The resulting Kohn-Sham system features two exchange-correlation (xc) potentials, a local xc potential and an xc contribution to the bias. For weakly coupled junctions the xc potentials exhibit steps in the density-current plane which are shown to be crucial to describe the Coulomb blockade diamonds. At small currents these steps emerge as the equilibrium xc discontinuity bifurcates. The formalism is applied to a model benzene junction, finding perfect agreement with the orthodox theory of Coulomb blockade.