Hydrodynamic relation in 2D Heisenberg antiferromagnet in a field
Abstract
The spin-stiffness s of a 2D Heisenberg antiferromagnet depends non-analytically on external magnetic field. We demonstrate that the hydrodynamic relation between s, the uniform susceptibility , and the spin-wave velocity c is not violated by such a behavior because similar non-analytic terms from all three quantities mutually cancel out. In this work, explicit expressions for the field-dependent spin stiffness and for the magnon velocity of the 2D square lattice antiferromagnet are obtained by direct calculation to order 1/S and in the whole range of magnetic fields.
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