The Heisenberg Antiferromagnet With a Low Concentration of Static Defects
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Quantum Physics
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Abstract
The static and dynamic response associated with a low concentration, x, of static defects in a Heisenberg antiferromagnet at zero temperature is analyzed within linearized spin‐wave theory. We obtain the dispersion relation for long‐wavelength spin waves in the form ω(q )= c ( x ) q + iγ( x ) q τ. Our results for c(x) agree with previous work, and in particular give c(x) = c(0)[1 + αx + O(x 2)] where the coefficient α, which can be related to the helicity modulus and the uniform perpendicular susceptibility, diverges in the limit d→2, where d is the spatial dimensionality. One major new result is that τ=d−1 for defects whose spin, S’, is different from that (S) of the host lattice and τ=d+1 when S’=S.