Interchain coupling model for quasi-one-dimensional π-conjugated organic ferromagnets

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Abstract
Two neighboring π-conjugated organic-polymer ferromagnetic chains are described individually by a Hamiltonian, which is the Su-Schrieffer-Heeger Hamiltonian added by the Hubbard electron-electron repulsion. In consideration of the topological structure of the system, the interchain coupling is taken into account as an interchain electron-transfer term, which is different with respect to different sites in chains. The splitting of energy levels with respect to different chains, the ferromagnetic order, and the dimerization are studied in detail. It is shown that in the high-spin ground state of the system, different configurations with interchain coupling will result in transfer of spin density between the main chain and side radical, and appropriate coupling strength stabilizes the high-spin ground state. However, as the coupling reaches a critical value, the energy gap disappears and the high-spin state does not exist. It is also found that the dimerization along the main chain varies with the interchain coupling.