QUANTUM CRITICAL PROPERTIES OF FERRIMAGNETIC HUBBARD CHAINS

We study inorganic and organic ferrimagnetic Hubbard chains at half-fi lling and in the strong coupling limit and show that, in the long-wave length regime, they are described by a one-dimensional (1D) nonlinear sigma model with an extra Wess-Zumino term. We then argue, based on a renormalization-group analysis, that these spin-1/2 AB(2) chains have quantum critical properties and belong to the same universality class as constrained classical 3D Heisenberg systems. For higher spins, the constraint is lifted but the critical behavior remains three dimension al.