MULTICHANNEL KONDO NECKLACE

A multichannel generalization of Doniach's Kondo-necklace model is formulated, and its phase diagram studied in the mean-field approximation. Our intention is to introduce the simplest possible model that displays some of the features expected from the overscreened Kondo lattice. The N conduction-electron channels are represented by N sets of pseudospins tau(j), j = 1,..., N, which are all antiferromagnetically coupled to a periodic array of Absolute value of S = 1/2 spins. Exploiting permutation symmetry in the channel index j allows us to write down the self-consistency equation for general N. For N > 2, we find that the critical temperature is rising with increasing Kondo interaction; we interpret this effect by pointing out that the Kondo coupling creates composite pseudospin objects that undergo an ordering transition. The relevance of our findings to the underlying fermionic multichannel problem is discussed.