A variational coupled-cluster study of magnon-density-wave excitations in quantum antiferromagnets
arXiv:cond-mat/0606813 · doi:10.1103/PhysRevB.74.212401
Abstract
We extend recently proposed variational coupled-cluster method to describe excitation states of quantum antiferromagnetic bipartite lattices. We reproduce the spin-wave excitations (i.e., magnons with spin ). In addition, we obtain a new, spin-zero excitation (magnon-density waves) which has been missing in all existing spin-wave theories. Within our approximation, this magnon-density-wave excitation has a nonzero energy gap in a cubic lattice and is gapless in a square lattice, similar to those charge-density-wave excitations (plasmons) in quantum electron gases.
5 pages, 1 figure