Holes in a quantum antiferromagnet: New approach and exact results

It is shown that holes on the A and B sublattices of a spin-s antiferromagnet behave as charges ±s coupled to a gauge field $a_{\mu }$(n), n being the local order parameter. This general formalism can be pursued very far in d=1 where the finite-hole-concentration problem is described by massless fermions coupled to the σ model. Many exact results follow: Holes superconduct, destroy the quasi-long-range order, and wipe out the Θ term which distinguishes between integer and half-integer models or describes bond-strength alternation.