New type of antiferromagnetic polaron and bipolaron in HTc - superconductors

The possibility of formation of a new type of polaron based on the quantum aniferromagnet (AF) model is reported. We take into account exchange interactions between localized d-d spins of the AF, as well as the p-d interaction of the AF with p-carriers. The energy minimum is found when maximum charge density occurs on every second spin. The formation of such ``comb''-like polarons results from the damping of quantum fluctuations and the appearance of Van Vleck-like staggered magnetization. Such polarons tend to form pairs coupled by an AF ``glue''.