Current spin polarization of a platform molecule with compression effect

Using the first-principles method,the spin-dependent transport properties of a novel platform molecule containing a freestanding molecular wire is investigated by simulating the spin-polarized scanning tunneling microscope experiment with Ni tip and Au substrate electrodes.Transport calculations show that the total current increases as the tip gradually approaches to the substrate,which is consistent with the conductance obtained from previous experiment.More interestingly,the spin polarization(SP)of current modulated by compression effect has the completely opposite trend to the total current.Transmission analyses reveal that the reduction of SP of current with compression process originates from the promotion of spin-down electron channel,which is controlled by deforming the molecule wire.In addition,the density of states shows that the SP of current is directly affected by the organic–ferromagnetic spinterface.The weak orbital hybridization between the Ni tip and propynyl of molecule results in high interfacial SP,whereas the breaking of the C≡C triple of propynyl in favor of the Ni–C–C bond induces the strong orbital hybridization and restrains the interfacial SP.This work proposes a new way to control and design the SP of current through organic–ferromagnetic spinterface using functional molecular platform.

Theoretical design of single-molecule NOR and XNOR logic gates by using transition metal dibenzotetraaza[14]annulenes

The idea of replacing traditional silicon-based electronic components with the ones assembled by organic molecules to further scale down the electric circuits has been attracting extensive research focuses.Among the molecularly assembled components,the design of molecular logic gates with simple structure and high Boolean computing speed remains a great challenge.Here,by using the state-of-the-art nonequilibrium Green’s function theory in conjugation with first-principles method,the spin transport properties of single-molecule junctions comprised of two serially connected transition metal dibenzotetraaza[14]annulenes(TM(DBTAA),TM=Fe,Co)sandwiched between two single-walled carbon nanotube electrodes are theoretically investigated.The numerical results show a close dependence of the spin-resolved current-voltage characteristics on spin configurations between the left and right molecular kernels and the kind of TM atom in TM(DBTAA)molecule.By taking advantage of spin degree of freedom of electrons,NOR or XNOR Boolean logic gates can be realized in Fe(DBTAA)and Co(DBTAA)junctions depending on the definitions of input and output signals.This work proposes a new kind of molecular logic gates and hence is helpful for further miniaturization of the electric circuits.