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Nontopological thermal solitons in isotropic ferromagnetic lattices

N. Theodorakopoulos
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Abstract

The paper deals with the properties of thermally excited solitons of the isotropic spin-$S$ ferromagnetic chain with nearest-neighbor logarithmic interactions. The exact statistical mechanics of the interacting soliton gas is developed for the general case (arbitrary $S$, temperature and magnetic field). At low temperatures the model's thermodynamics coincides with that of the Heisenberg model. We present analytical approximations of the leading-order asymptotic behavior of the energy in three limiting cases: (a) zero field, low temperature, classical limit; (b) zero field, $T\to 0$, $S$ finite (quantum limit); (c) zero field, high temperature, classical limit. Cases (a) and (c) are examples of a dense gas of [non-topological] solitons; results are in agreement with those obtained by the transfer integral method. Case (b) illustrates the behavior of a dilute, yet strongly interacting soliton gas; results for the thermodynamics are very close to (but not identical with) spin-wave and/or Bethe-{\it Ansatz} predictions.

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N. Theodorakopoulos. 1995-06-14. Nontopological thermal solitons in isotropic ferromagnetic lattices. https://doi.org/10.1103/physrevb.52.9507

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