Abstract
The ability to control the spin-transport properties of a molecule
bridging conducting electrodes is of paramount importance to molecular
spintronics. Quantum interference can play an important role in allowing
or forbidding electrons from passing through a system. In this work, the
spin-transport properties of a polyacetylene chain bridging zigzag
graphene nanoribbons (ZGNRs) are studied with nonequilibrium Greens
function calculations performed within the density functional theory
framework (NEGF-DFT). ZGNR electrodes have inherent spin polarization
along their edges, which causes a splitting between the properties of
spin-up and spin-down electrons in these systems. Upon adding an
imidazole donor group and a pyridine acceptor group to the polyacetylene
chain, this causes destructive interference features in the electron
transmission spectrum. Particularly, the donor group causes a large
antiresonance dip in transmission at the Fermi energy EF of the
electrodes. The application of a gate is investigated and found to
provide control over the energy position of this feature making it
possible to turn this phenomenon on and off. The currentvoltage (IV)
characteristics of this system are also calculated, showing near ohmic
scaling for spin-up but negative differential resistance (NDR) for
spin-down.
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