Bosonic mean-field theory for frustrated Heisenberg antiferromagnets in two dimensions

Abstract

We use a recently developed bosonic mean-field theory to study the ordered ground states of frustrated Heisenberg antiferromagnets in two dimensions. We emphasize the role of condensates in satisfying the mean-field variational equations and their relation to spin-correlation functions at low temperatures. This mean-field theory is closely related to a spin-wave theory that enables us to obtain the spin-wave spectrum easily (without any rotation of axes) for an entire class of three-dimensionally ordered states. For the frustrated Heisenberg antiferromagnet on a triangular lattice, we use this theory to compute the spin-wave spectrum for all values of J₂/J₁ and demonstrate the phenomenon of order from disorder.