Anuradha Jagannathan, Attila Szallas
We show that fluctuations of geometrical connectivity can give rise to a Casimir type attractive or repulsive force in a two dimensional Heisenberg antiferromagnet. The type of fluctuation that we consider, called a phason flip, is well known in quasicrystals, but less so in periodic structures. As the classical ground state energy of the antiferromagnet is unaffected by this type of fluctuation, energy changes are purely of quantum origin. We calculate the effective interaction between two parallel domain walls, defining a slab of thickness d, in such an antiferromagnet within linear spin wave theory. The interaction is anisotropic, and for a particular orientation of the slab we find that it decays as 1/d, thus, more slowly than the electromagnetic Casimir effect in the same geometry.
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http://arxiv.org/abs/1210.4442
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