An Upper Bound for the Spin-Wave Spectrum of the Heisenberg Antiferromagnet

抄録

We study the spin-wave spectrum of the Heisenberg antiferromagnet on a bipartite lattice. The spin-wave spectrum on a Néel-ordered ground state is bounded as ε (k)≤ c| k|, where c gives an upper bound for the spin-wave velocity. In the large-S limit, the upper bound c coincides with the result of the spin-wave theory.