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A variational coupled-cluster study of magnon-density-wave excitations in quantum antiferromagnets

Y. Xian
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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 $\pm 1$). 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.

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Y. Xian. 2006-07-04. A variational coupled-cluster study of magnon-density-wave excitations in quantum antiferromagnets. https://doi.org/10.1103/physrevb.74.212401

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