Co-operative Kondo effect in the two-channel Kondo lattice

We examine how the properties of a single-channel Kondo lattice model are modified by additional screening channels. Contrary to current wisdom, additional screening channels appear to constitute a relevant perturbation which destabilizes the Fermi liquid. This instability involves two stages. When a heavy Fermi surface develops, it generates zero modes for Kondo singlets to fluctuate between screening channels of different symmetry, producing a divergent composite pair susceptibility. Additional screening channels couple to these divergent fluctuations, promoting an instability into a superconducting state with long-range composite order. We discuss possible implications for heavy fermion superconductivity. [S0163-1829(99)04629-9].