Spin-polarized electron transport through magnetic poly-BIPO molecule: the role of soliton-antisoliton separation

Spin-polarized transport through a one-dimensional metal/poly-BIPO/metal model junction with the soliton-antisoliton separation is investigated. Nonlinear spin and charge densities are considered in magnetic poly-BIPO molecule, as a neutral soliton and charged antisoliton with different separations. The calculations are performed based on Su-Schrieffer-Heeger Hamiltonian which is extended with Heisenberg and Hubbard Hamiltonians to include the spin and electron-electron interactions. The spin-dependent transport properties are obtained within the framework of the Landauer-Büttiker formalism based on Green's function theory. This study demonstrates the reduction in current and spin polarization as the separation between soliton and antisoliton centers is increased. We have found that when the soliton-antisoliton separation is less than 14 sites, the spin polarization is almost 100 % plato, over the voltage ranges more than 0.3 V. Also the energy differences between the soliton-antisoliton mid-gap states for up- and down-spin electrons and the Fermi energy of the system are reduced. However, for the soliton-antisoliton separation lengths more than 14 sites, these quantities tend to constant values with enhancement of the distance between the excitation centers. (author)