Effects of spin–orbit coupling on the conductance of molecules contacted with goldelectrodes

Abstract

The effects of spin–orbit coupling on the conductance of molecular devices made with Auelectrodes are investigated using a fully self-consistent ab initio approach, which combinesthe non-equilibrium Green’s function formalism with density functional theory. In general,we find that the extent to which spin–orbit interaction affects the transport depends on thespecific materials system investigated and on the dimensionality of the electrodes. Forone-dimensional electrodes contacting benzene–dithiol molecules the spin–orbit couplinginduces changes in the low-bias conductance up to about 20%. These originate mostly fromchanges in the electrode band structure. In contrast when three-dimensional electrodes areused, the bands near the Fermi level are only weakly modified by spin–orbit coupling andmost of the variations are due to symmetry changes at the molecule–electrodeinterface. For this reason strongly coupled systems, such as Au atomic nanowiressandwiched between Au (100) surfaces and benzene–dithiol molecules bonded at theAu (111) hollow site, are rather insensitive to spin–orbit effects. In contrast, injunctions where the coupling between the molecule and the electrodes is weaker,as in the case of benzene–dithiol bonded to Au (111) at adatom positions, thetransmission coefficient at the Fermi level can be modified by as much as 14%.