Bipolaron formation in the presence of magnetic impurities

The formation of bipolarons in the presence of magnetic impurities is studied theoretically. We use the extended Hubbard Su–Schrieffer–Heeger (SSH) model with Brazovskii–Kirova and Kondo interaction terms. Parameters are chosen suitably for cis-polyacetylene. A Quantum Monte Carlo (QMC) algorithm is used to study the equilibrium lattice structure and charge distribution as a function of doping level and Kondo exchange integral. The magnetic impurities can have a destructive effect on bipolaron stability, instead favouring the two polaron configuration. However by suitably adjusting the doping level, bipolarons can be stabilized over a wide range of impurity strength.